Slice 3 wave A: tabs model, model selector, cache delete, localStorage

- features/tabs: pure tab-workspace reducer (create/select/close/setModel/
  setTitle/deriveTitle, draft=null active) + injected-persistence runes store
- features/chat: mutable per-tab model (setModel) + delta routing guard
  (ignore foreign conversationId) + ModelSelector.svelte + DaisyUI chat bubbles
  / composer (keeps streaming <details> keying fix)
- features/conversation-cache: surface delete(conversationId) on the wrapper
  for tab-close local-forget
- adapters/local-storage: generic injected JSON localStore<T> (quota/corrupt-safe)

Verified: svelte-check 0/0, vitest 273, biome clean, build ok.

8 files changed, 190 insertions, 21 deletions

diff --git a/src/features/chat/index.ts b/src/features/chat/index.ts
index 71851de..f1e8e29 100644
--- a/src/features/chat/index.ts
+++ b/src/features/chat/index.ts
@@ -4,3 +4,4 @@ export type { ChatStore, ChatStoreDependencies } from "./store.svelte";
 export { createChatStore } from "./store.svelte";
 export { default as ChatView } from "./ui/ChatView.svelte";
 export { default as Composer } from "./ui/Composer.svelte";
+export { default as ModelSelector } from "./ui/ModelSelector.svelte";
diff --git a/src/features/chat/store.svelte.ts b/src/features/chat/store.svelte.ts
index b7405cf..e997f49 100644
--- a/src/features/chat/store.svelte.ts
+++ b/src/features/chat/store.svelte.ts
@@ -28,8 +28,10 @@ export interface ChatStore {
 	readonly chunks: readonly RenderedChunk[];
 	readonly pendingSync: boolean;
 	readonly error: string | null;
+	readonly model: string | undefined;
 	handleDelta(msg: ChatDeltaMessage | ChatErrorMessage): void;
 	send(text: string): void;
+	setModel(model: string): void;
 	load(): Promise<void>;
 	dispose(): void;
 }
@@ -38,6 +40,7 @@ export function createChatStore(deps: ChatStoreDependencies): ChatStore {
 	let transcript = $state<TranscriptState>(initialState());
 	let _pendingSync = $state(false);
 	let _error = $state<string | null>(null);
+	let _model = $state<string | undefined>(deps.model);
 	let disposed = false;
 
 	async function syncTail(): Promise<void> {
@@ -69,12 +72,21 @@ export function createChatStore(deps: ChatStoreDependencies): ChatStore {
 		get error(): string | null {
 			return _error;
 		},
+		get model(): string | undefined {
+			return _model;
+		},
 
 		handleDelta(msg: ChatDeltaMessage | ChatErrorMessage): void {
 			if (msg.type === "chat.error") {
+				if (msg.conversationId !== undefined && msg.conversationId !== deps.conversationId) {
+					return;
+				}
 				_error = msg.message;
 				return;
 			}
+			if (msg.event.conversationId !== deps.conversationId) {
+				return;
+			}
 			transcript = foldEvent(transcript, msg.event);
 			if (transcript.sealedTurnId !== null) {
 				void syncTail();
@@ -86,11 +98,15 @@ export function createChatStore(deps: ChatStoreDependencies): ChatStore {
 				type: "chat.send",
 				conversationId: deps.conversationId,
 				message: text,
-				...(deps.model !== undefined ? { model: deps.model } : {}),
+				...(_model !== undefined ? { model: _model } : {}),
 			};
 			deps.transport.send(msg);
 		},
 
+		setModel(model: string): void {
+			_model = model;
+		},
+
 		async load(): Promise<void> {
 			const cached = await deps.cache.load(deps.conversationId);
 			if (cached.length > 0) {
diff --git a/src/features/chat/store.test.ts b/src/features/chat/store.test.ts
index 77a53c9..4ec40a9 100644
--- a/src/features/chat/store.test.ts
+++ b/src/features/chat/store.test.ts
@@ -347,4 +347,93 @@ describe("createChatStore", () => {
 
 		store.dispose();
 	});
+
+	it("setModel changes the model used by the next send", () => {
+		const transport = createFakeTransport();
+		const historySync = createFakeHistorySync();
+		const cache = createFakeCache();
+		const store = createChatStore({
+			conversationId: CONV_ID,
+			model: "openai/gpt-4",
+			transport: transport.impl,
+			historySync: historySync.impl,
+			cache: cache.impl,
+		});
+
+		store.send("First");
+		expect(transport.sent[0]?.model).toBe("openai/gpt-4");
+
+		store.setModel("anthropic/claude-3");
+		store.send("Second");
+		expect(transport.sent[1]?.model).toBe("anthropic/claude-3");
+
+		store.dispose();
+	});
+
+	it("setModel from undefined to a model", () => {
+		const transport = createFakeTransport();
+		const historySync = createFakeHistorySync();
+		const cache = createFakeCache();
+		const store = createChatStore({
+			conversationId: CONV_ID,
+			transport: transport.impl,
+			historySync: historySync.impl,
+			cache: cache.impl,
+		});
+
+		store.send("First");
+		expect(transport.sent[0]).not.toHaveProperty("model");
+
+		store.setModel("openai/gpt-4o");
+		store.send("Second");
+		expect(transport.sent[1]?.model).toBe("openai/gpt-4o");
+
+		store.dispose();
+	});
+
+	it("handleDelta ignores a chat.delta for a different conversationId", () => {
+		const transport = createFakeTransport();
+		const historySync = createFakeHistorySync();
+		const cache = createFakeCache();
+		const store = createChatStore({
+			conversationId: CONV_ID,
+			transport: transport.impl,
+			historySync: historySync.impl,
+			cache: cache.impl,
+		});
+
+		store.handleDelta(
+			deltaEvent({ type: "turn-start", conversationId: "other-conv", turnId: "t1" }),
+		);
+		store.handleDelta(
+			deltaEvent({
+				type: "text-delta",
+				conversationId: "other-conv",
+				turnId: "t1",
+				delta: "Should be ignored",
+			}),
+		);
+
+		expect(store.messages).toHaveLength(0);
+
+		store.dispose();
+	});
+
+	it("handleDelta ignores a chat.error for a different conversationId", () => {
+		const transport = createFakeTransport();
+		const historySync = createFakeHistorySync();
+		const cache = createFakeCache();
+		const store = createChatStore({
+			conversationId: CONV_ID,
+			transport: transport.impl,
+			historySync: historySync.impl,
+			cache: cache.impl,
+		});
+
+		store.handleDelta({ type: "chat.error", conversationId: "other-conv", message: "Wrong conv" });
+
+		expect(store.error).toBeNull();
+
+		store.dispose();
+	});
 });
diff --git a/src/features/chat/test-helpers.ts b/src/features/chat/test-helpers.ts
index e58818a..d37b59e 100644
--- a/src/features/chat/test-helpers.ts
+++ b/src/features/chat/test-helpers.ts
@@ -75,6 +75,9 @@ export function createFakeCache(): FakeCache {
 			async evictIfOverBudget() {
 				return [];
 			},
+			async delete(conversationId) {
+				store.delete(conversationId);
+			},
 		},
 	};
 }
diff --git a/src/features/chat/ui.test.ts b/src/features/chat/ui.test.ts
index aebb97c..ac8f640 100644
--- a/src/features/chat/ui.test.ts
+++ b/src/features/chat/ui.test.ts
@@ -4,6 +4,7 @@ import { describe, expect, it, vi } from "vitest";
 import type { RenderedChunk } from "../../core/chunks";
 import ChatView from "./ui/ChatView.svelte";
 import Composer from "./ui/Composer.svelte";
+import ModelSelector from "./ui/ModelSelector.svelte";
 
 describe("ChatView", () => {
 	it("renders a message's text chunk", () => {
@@ -144,8 +145,8 @@ describe("ChatView", () => {
 
 		render(ChatView, { props: { chunks } });
 
-		const article = screen.getByText("Streaming...").closest("article");
-		expect(article).toHaveClass("message--provisional");
+		const bubble = screen.getByText("Streaming...").closest(".chat-bubble");
+		expect(bubble).toHaveClass("opacity-50");
 	});
 
 	it("renders empty transcript", () => {
@@ -260,3 +261,38 @@ describe("Composer", () => {
 		expect(onSend).not.toHaveBeenCalled();
 	});
 });
+
+describe("ModelSelector", () => {
+	it("renders the options and current selection", () => {
+		const models = ["openai/gpt-4", "anthropic/claude-3", "google/gemini"];
+		render(ModelSelector, {
+			props: { models, selected: "anthropic/claude-3", onSelect: vi.fn() },
+		});
+
+		const select = screen.getByRole("combobox", { name: "Model selector" });
+		expect(select).toBeInTheDocument();
+		expect(select).toHaveValue("anthropic/claude-3");
+
+		const options = screen.getAllByRole("option");
+		expect(options).toHaveLength(3);
+		expect(options[0]).toHaveValue("openai/gpt-4");
+		expect(options[1]).toHaveValue("anthropic/claude-3");
+		expect(options[2]).toHaveValue("google/gemini");
+	});
+
+	it("calls onSelect on change", async () => {
+		const onSelect = vi.fn();
+		const user = userEvent.setup();
+		const models = ["openai/gpt-4", "anthropic/claude-3"];
+
+		render(ModelSelector, {
+			props: { models, selected: "openai/gpt-4", onSelect },
+		});
+
+		const select = screen.getByRole("combobox", { name: "Model selector" });
+		await user.selectOptions(select, "anthropic/claude-3");
+
+		expect(onSelect).toHaveBeenCalledTimes(1);
+		expect(onSelect).toHaveBeenCalledWith("anthropic/claude-3");
+	});
+});
diff --git a/src/features/chat/ui/ChatView.svelte b/src/features/chat/ui/ChatView.svelte
index ce66798..cb6069b 100644
--- a/src/features/chat/ui/ChatView.svelte
+++ b/src/features/chat/ui/ChatView.svelte
@@ -4,14 +4,16 @@
 	let { chunks }: { chunks: readonly RenderedChunk[] } = $props();
 </script>
 
-<div class="chat-transcript" role="log" aria-live="polite">
+<div class="flex flex-col gap-2 p-4" role="log" aria-live="polite">
 	{#each chunks as rendered, i (rendered.seq != null ? `c${rendered.seq}` : `p${i}`)}
-		<article
-			class="message message--{rendered.role}"
-			class:message--provisional={rendered.provisional}
-		>
-			<header class="message__role">{rendered.role}</header>
-			<div class="message__content">
+		<div class="chat {rendered.role === 'user' ? 'chat-start' : 'chat-end'}">
+			<div class="chat-header text-xs opacity-70">{rendered.role}</div>
+			<div
+				class="chat-bubble"
+				class:chat-bubble-primary={rendered.role === "user"}
+				class:chat-bubble-secondary={rendered.role === "assistant"}
+				class:opacity-50={rendered.provisional}
+			>
 				{#if rendered.chunk.type === "text"}
 					<p>{rendered.chunk.text}</p>
 				{:else if rendered.chunk.type === "thinking"}
@@ -20,26 +22,26 @@
 						<p>{rendered.chunk.text}</p>
 					</details>
 				{:else if rendered.chunk.type === "tool-call"}
-					<div class="tool-call">
+					<div class="text-sm">
 						<strong>{rendered.chunk.toolName}</strong>
-						<pre>{JSON.stringify(rendered.chunk.input, null, 2)}</pre>
+						<pre class="text-xs mt-1">{JSON.stringify(rendered.chunk.input, null, 2)}</pre>
 					</div>
 				{:else if rendered.chunk.type === "tool-result"}
-					<div class="tool-result" class:tool-result--error={rendered.chunk.isError}>
+					<div class="text-sm" class:text-error={rendered.chunk.isError}>
 						<strong>{rendered.chunk.toolName}</strong>
-						<pre>{rendered.chunk.content}</pre>
+						<pre class="text-xs mt-1">{rendered.chunk.content}</pre>
 					</div>
 				{:else if rendered.chunk.type === "error"}
-					<div class="error" role="alert">
+					<div class="text-error" role="alert">
 						{rendered.chunk.message}
 						{#if rendered.chunk.code}
-							<span class="error__code">[{rendered.chunk.code}]</span>
+							<span class="text-xs opacity-70">[{rendered.chunk.code}]</span>
 						{/if}
 					</div>
 				{:else if rendered.chunk.type === "system"}
-					<div class="system">{rendered.chunk.text}</div>
+					<div class="text-sm opacity-70">{rendered.chunk.text}</div>
 				{/if}
 			</div>
-		</article>
+		</div>
 	{/each}
 </div>
diff --git a/src/features/chat/ui/Composer.svelte b/src/features/chat/ui/Composer.svelte
index dc71e11..3762340 100644
--- a/src/features/chat/ui/Composer.svelte
+++ b/src/features/chat/ui/Composer.svelte
@@ -18,16 +18,16 @@
 	}
 </script>
 
-<form class="composer" onsubmit={prevent => { prevent.preventDefault(); handleSubmit(); }}>
+<form class="flex gap-2 p-4" onsubmit={(e) => { e.preventDefault(); handleSubmit(); }}>
 	<textarea
-		class="composer__input"
+		class="textarea textarea-bordered flex-1"
 		bind:value={text}
 		onkeydown={handleKeydown}
 		placeholder="Type a message..."
 		rows="3"
 		aria-label="Message input"
 	></textarea>
-	<button class="composer__send" type="submit" disabled={text.trim().length === 0}>
+	<button class="btn btn-primary" type="submit" disabled={text.trim().length === 0}>
 		Send
 	</button>
 </form>
diff --git a/src/features/chat/ui/ModelSelector.svelte b/src/features/chat/ui/ModelSelector.svelte
new file mode 100644
index 0000000..3e25ec3
--- /dev/null
+++ b/src/features/chat/ui/ModelSelector.svelte
@@ -0,0 +1,22 @@
+<script lang="ts">
+	let {
+		models,
+		selected,
+		onSelect,
+	}: {
+		models: readonly string[];
+		selected: string;
+		onSelect: (model: string) => void;
+	} = $props();
+</script>
+
+<select
+	class="select"
+	value={selected}
+	onchange={(e) => onSelect(e.currentTarget.value)}
+	aria-label="Model selector"
+>
+	{#each models as model (model)}
+		<option value={model}>{model}</option>
+	{/each}
+</select>