Slice 2 wave 1: transcript reducer, wire conformance, ws chat, cache core

- core/chunks: the one pure transcript reducer (foldEvent live deltas +
  applyHistory seq-keyed reconcile + selectChunks/selectMessages); 27 tests
- core/wire: FE-side contract-conformance exhaustiveness guards + drift smoke
  tests over wire/transport-contract unions (§2.9 drift signal); 10 tests
- adapters/ws: additively multiplex chat.send/chat.delta/chat.error on the
  existing surface socket (onChat + widened send); surface API unchanged
- features/conversation-cache: pure reconcileCache/nextSinceSeq/selectEvictions
  + ConversationChunkStore port + injected createConversationCache; 26 tests

Verified green: svelte-check 0/0, vitest 169, biome clean, build ok.

1 files changed, 406 insertions, 0 deletions

diff --git a/src/core/chunks/reducer.test.ts b/src/core/chunks/reducer.test.ts
new file mode 100644
index 0000000..f83edb4
--- /dev/null
+++ b/src/core/chunks/reducer.test.ts
@@ -0,0 +1,406 @@
+import type {
+	StoredChunk,
+	TurnDoneEvent,
+	TurnErrorEvent,
+	TurnReasoningDeltaEvent,
+	TurnSealedEvent,
+	TurnStartEvent,
+	TurnTextDeltaEvent,
+	TurnToolCallEvent,
+	TurnToolResultEvent,
+	TurnUsageEvent,
+} from "@dispatch/wire";
+import { describe, expect, it } from "vitest";
+import { applyHistory, foldEvent, initialState } from "./reducer";
+import { selectChunks, selectMessages } from "./selectors";
+
+const turnStart = (turnId: string): TurnStartEvent => ({
+	type: "turn-start",
+	conversationId: "c1",
+	turnId,
+});
+
+const textDelta = (turnId: string, delta: string): TurnTextDeltaEvent => ({
+	type: "text-delta",
+	conversationId: "c1",
+	turnId,
+	delta,
+});
+
+const reasoningDelta = (turnId: string, delta: string): TurnReasoningDeltaEvent => ({
+	type: "reasoning-delta",
+	conversationId: "c1",
+	turnId,
+	delta,
+});
+
+const toolCall = (
+	turnId: string,
+	toolCallId: string,
+	toolName: string,
+	input: unknown,
+): TurnToolCallEvent => ({
+	type: "tool-call",
+	conversationId: "c1",
+	turnId,
+	toolCallId,
+	toolName,
+	input,
+});
+
+const toolResult = (
+	turnId: string,
+	toolCallId: string,
+	toolName: string,
+	content: string,
+): TurnToolResultEvent => ({
+	type: "tool-result",
+	conversationId: "c1",
+	turnId,
+	toolCallId,
+	toolName,
+	content,
+	isError: false,
+});
+
+const usageEvent = (turnId: string, inputTokens: number, outputTokens: number): TurnUsageEvent => ({
+	type: "usage",
+	conversationId: "c1",
+	turnId,
+	usage: { inputTokens, outputTokens },
+});
+
+const errorEvent = (turnId: string, message: string, code?: string): TurnErrorEvent =>
+	code !== undefined
+		? { type: "error", conversationId: "c1", turnId, message, code }
+		: { type: "error", conversationId: "c1", turnId, message };
+
+const doneEvent = (turnId: string): TurnDoneEvent => ({
+	type: "done",
+	conversationId: "c1",
+	turnId,
+	reason: "stop",
+});
+
+const turnSealed = (turnId: string): TurnSealedEvent => ({
+	type: "turn-sealed",
+	conversationId: "c1",
+	turnId,
+});
+
+const storedChunk = (
+	seq: number,
+	role: "user" | "assistant" | "tool" | "system",
+	chunk: StoredChunk["chunk"],
+): StoredChunk => ({
+	seq,
+	role,
+	chunk,
+});
+
+describe("initialState", () => {
+	it("initial state is empty", () => {
+		const s = initialState();
+		expect(s.committed).toEqual([]);
+		expect(s.provisional).toEqual([]);
+		expect(s.accumulating).toBeNull();
+		expect(s.currentTurnId).toBeNull();
+		expect(s.latestUsage).toBeNull();
+		expect(s.sealedTurnId).toBeNull();
+	});
+});
+
+describe("foldEvent — text-delta", () => {
+	it("text-delta accumulates into one TextChunk", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, textDelta("t1", "hello"));
+		expect(s.accumulating).toEqual({ kind: "text", text: "hello" });
+		expect(s.provisional).toEqual([]);
+	});
+
+	it("successive text-deltas extend the same provisional chunk", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, textDelta("t1", "hello "));
+		s = foldEvent(s, textDelta("t1", "world"));
+		expect(s.accumulating).toEqual({ kind: "text", text: "hello world" });
+		expect(s.provisional).toEqual([]);
+	});
+
+	it("text-delta after reasoning-delta flushes thinking and starts text", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, reasoningDelta("t1", "thinking..."));
+		s = foldEvent(s, textDelta("t1", "answer"));
+		expect(s.accumulating).toEqual({ kind: "text", text: "answer" });
+		expect(s.provisional).toHaveLength(1);
+		expect(s.provisional[0]?.chunk).toEqual({ type: "thinking", text: "thinking..." });
+		expect(s.provisional[0]?.role).toBe("assistant");
+	});
+});
+
+describe("foldEvent — reasoning-delta", () => {
+	it("reasoning-delta yields a thinking chunk", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, reasoningDelta("t1", "hmm"));
+		expect(s.accumulating).toEqual({ kind: "thinking", text: "hmm" });
+	});
+
+	it("successive reasoning-deltas extend the same chunk", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, reasoningDelta("t1", "hmm "));
+		s = foldEvent(s, reasoningDelta("t1", "ok"));
+		expect(s.accumulating).toEqual({ kind: "thinking", text: "hmm ok" });
+	});
+});
+
+describe("foldEvent — tool-call then tool-result", () => {
+	it("tool-call then tool-result render in order", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, toolCall("t1", "tc1", "bash", { cmd: "ls" }));
+		s = foldEvent(s, toolResult("t1", "tc1", "bash", "file.txt"));
+		expect(s.provisional).toHaveLength(2);
+		expect(s.provisional[0]?.role).toBe("assistant");
+		expect(s.provisional[0]?.chunk).toEqual({
+			type: "tool-call",
+			toolCallId: "tc1",
+			toolName: "bash",
+			input: { cmd: "ls" },
+		});
+		expect(s.provisional[1]?.role).toBe("tool");
+		expect(s.provisional[1]?.chunk).toEqual({
+			type: "tool-result",
+			toolCallId: "tc1",
+			toolName: "bash",
+			content: "file.txt",
+			isError: false,
+		});
+	});
+
+	it("tool-call flushes accumulating text", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, textDelta("t1", "let me check"));
+		s = foldEvent(s, toolCall("t1", "tc1", "bash", {}));
+		expect(s.provisional).toHaveLength(2);
+		expect(s.provisional[0]?.chunk).toEqual({ type: "text", text: "let me check" });
+		expect(s.provisional[1]?.chunk).toMatchObject({ type: "tool-call", toolCallId: "tc1" });
+		expect(s.accumulating).toBeNull();
+	});
+});
+
+describe("foldEvent — turn-sealed", () => {
+	it("turn-sealed sets sealedTurnId", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, textDelta("t1", "hi"));
+		s = foldEvent(s, turnSealed("t1"));
+		expect(s.sealedTurnId).toBe("t1");
+		expect(s.accumulating).toBeNull();
+		expect(s.provisional).toHaveLength(1);
+		expect(s.provisional[0]?.chunk).toEqual({ type: "text", text: "hi" });
+	});
+});
+
+describe("foldEvent — usage", () => {
+	it("stores latest usage", () => {
+		let s = initialState();
+		s = foldEvent(s, usageEvent("t1", 100, 50));
+		expect(s.latestUsage).toEqual({ inputTokens: 100, outputTokens: 50 });
+	});
+
+	it("overwrites previous usage", () => {
+		let s = initialState();
+		s = foldEvent(s, usageEvent("t1", 100, 50));
+		s = foldEvent(s, usageEvent("t1", 200, 80));
+		expect(s.latestUsage).toEqual({ inputTokens: 200, outputTokens: 80 });
+	});
+});
+
+describe("foldEvent — error", () => {
+	it("creates error chunk with code", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, errorEvent("t1", "bad", "E001"));
+		expect(s.provisional).toHaveLength(1);
+		expect(s.provisional[0]?.chunk).toEqual({ type: "error", message: "bad", code: "E001" });
+		expect(s.provisional[0]?.role).toBe("assistant");
+	});
+
+	it("creates error chunk without code", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, errorEvent("t1", "bad"));
+		expect(s.provisional).toHaveLength(1);
+		expect(s.provisional[0]?.chunk).toEqual({ type: "error", message: "bad" });
+	});
+});
+
+describe("foldEvent — done", () => {
+	it("flushes accumulating chunk on done", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, textDelta("t1", "hello"));
+		s = foldEvent(s, doneEvent("t1"));
+		expect(s.accumulating).toBeNull();
+		expect(s.provisional).toHaveLength(1);
+		expect(s.provisional[0]?.chunk).toEqual({ type: "text", text: "hello" });
+	});
+});
+
+describe("foldEvent — status and tool-output", () => {
+	it("status is a no-op", () => {
+		const s = initialState();
+		const next = foldEvent(s, { type: "status", conversationId: "c1", status: "running" });
+		expect(next).toBe(s);
+	});
+
+	it("tool-output is a no-op", () => {
+		const s = initialState();
+		const next = foldEvent(s, {
+			type: "tool-output",
+			conversationId: "c1",
+			turnId: "t1",
+			toolCallId: "tc1",
+			data: "output",
+			stream: "stdout",
+		});
+		expect(next).toBe(s);
+	});
+});
+
+describe("applyHistory", () => {
+	it("orders committed chunks by seq", () => {
+		const s = initialState();
+		const chunks = [
+			storedChunk(3, "assistant", { type: "text", text: "c" }),
+			storedChunk(1, "user", { type: "text", text: "a" }),
+			storedChunk(2, "assistant", { type: "text", text: "b" }),
+		];
+		const next = applyHistory(s, chunks);
+		expect(next.committed.map((c) => c.seq)).toEqual([1, 2, 3]);
+	});
+
+	it("is idempotent on duplicate seqs", () => {
+		let s = initialState();
+		const batch1 = [
+			storedChunk(1, "user", { type: "text", text: "a" }),
+			storedChunk(2, "assistant", { type: "text", text: "b" }),
+		];
+		s = applyHistory(s, batch1);
+		const batch2 = [
+			storedChunk(2, "assistant", { type: "text", text: "b" }),
+			storedChunk(3, "assistant", { type: "text", text: "c" }),
+		];
+		s = applyHistory(s, batch2);
+		expect(s.committed.map((c) => c.seq)).toEqual([1, 2, 3]);
+		expect(s.committed).toHaveLength(3);
+	});
+
+	it("supersedes & clears provisional once committed", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, textDelta("t1", "hello"));
+		s = foldEvent(s, turnSealed("t1"));
+		expect(s.provisional).toHaveLength(1);
+		expect(s.sealedTurnId).toBe("t1");
+
+		s = applyHistory(s, [storedChunk(1, "assistant", { type: "text", text: "hello" })]);
+		expect(s.provisional).toEqual([]);
+		expect(s.accumulating).toBeNull();
+		expect(s.sealedTurnId).toBeNull();
+		expect(s.committed).toHaveLength(1);
+	});
+
+	it("keeps provisional and accumulating when sealedTurnId is null", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, textDelta("t1", "wip"));
+		s = foldEvent(s, doneEvent("t1"));
+		s = applyHistory(s, [storedChunk(1, "user", { type: "text", text: "q" })]);
+		expect(s.provisional).toHaveLength(1);
+		expect(s.committed).toHaveLength(1);
+	});
+
+	it("merges new history into existing committed", () => {
+		let s = initialState();
+		s = applyHistory(s, [storedChunk(1, "user", { type: "text", text: "a" })]);
+		s = applyHistory(s, [storedChunk(2, "assistant", { type: "text", text: "b" })]);
+		expect(s.committed).toHaveLength(2);
+		expect(s.committed.map((c) => c.seq)).toEqual([1, 2]);
+	});
+});
+
+describe("selectChunks", () => {
+	it("selectChunks marks provisional with seq null", () => {
+		let s = initialState();
+		s = applyHistory(s, [storedChunk(1, "user", { type: "text", text: "q" })]);
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, textDelta("t1", "wip"));
+		const chunks = selectChunks(s);
+		expect(chunks).toHaveLength(2);
+		expect(chunks[0]?.seq).toBe(1);
+		expect(chunks[0]?.provisional).toBe(false);
+		expect(chunks[1]?.seq).toBeNull();
+		expect(chunks[1]?.provisional).toBe(true);
+	});
+
+	it("returns empty for empty state", () => {
+		expect(selectChunks(initialState())).toEqual([]);
+	});
+
+	it("includes accumulating chunk as provisional", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, textDelta("t1", "building..."));
+		const chunks = selectChunks(s);
+		expect(chunks).toHaveLength(1);
+		expect(chunks[0]?.seq).toBeNull();
+		expect(chunks[0]?.provisional).toBe(true);
+		expect(chunks[0]?.chunk).toEqual({ type: "text", text: "building..." });
+	});
+});
+
+describe("selectMessages", () => {
+	it("selectMessages groups consecutive same-role chunks", () => {
+		let s = initialState();
+		s = applyHistory(s, [
+			storedChunk(1, "user", { type: "text", text: "q1" }),
+			storedChunk(2, "user", { type: "text", text: "q2" }),
+			storedChunk(3, "assistant", { type: "text", text: "a1" }),
+			storedChunk(4, "assistant", { type: "text", text: "a2" }),
+			storedChunk(5, "user", { type: "text", text: "q3" }),
+		]);
+		const msgs = selectMessages(s);
+		expect(msgs).toHaveLength(3);
+		expect(msgs[0]?.role).toBe("user");
+		expect(msgs[0]?.chunks).toHaveLength(2);
+		expect(msgs[1]?.role).toBe("assistant");
+		expect(msgs[1]?.chunks).toHaveLength(2);
+		expect(msgs[2]?.role).toBe("user");
+		expect(msgs[2]?.chunks).toHaveLength(1);
+	});
+
+	it("returns empty for empty state", () => {
+		expect(selectMessages(initialState())).toEqual([]);
+	});
+
+	it("mixes committed and provisional in messages", () => {
+		let s = initialState();
+		s = applyHistory(s, [storedChunk(1, "user", { type: "text", text: "q" })]);
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, textDelta("t1", "a1"));
+		s = foldEvent(s, textDelta("t1", "a2"));
+		const msgs = selectMessages(s);
+		expect(msgs).toHaveLength(2);
+		expect(msgs[0]?.role).toBe("user");
+		expect(msgs[0]?.chunks).toHaveLength(1);
+		expect(msgs[1]?.role).toBe("assistant");
+		expect(msgs[1]?.chunks).toHaveLength(1);
+		expect(msgs[1]?.chunks[0]).toEqual({ type: "text", text: "a1a2" });
+	});
+});