feat(chat): group batched tool calls into one DaisyUI list

Consume the backend's new stepId grouping key (wire/transport-contract
0.1.0 -> 0.2.0). foldEvent copies event.stepId onto live tool chunks so
live and replay group identically. New pure selector groupRenderedChunks
(core/chunks) folds a step's 2+ tool calls into one tool-batch group,
pairing each call with its result by toolCallId; single/no-stepId calls
stay as cards. ChatView renders a batch as a DaisyUI list (list-row per
pair). Fixtures updated for the now-required event stepId.

1 files changed, 56 insertions, 0 deletions

diff --git a/src/features/chat/ui.test.ts b/src/features/chat/ui.test.ts
index 2099257..43822a7 100644
--- a/src/features/chat/ui.test.ts
+++ b/src/features/chat/ui.test.ts
@@ -1,3 +1,4 @@
+import type { StepId } from "@dispatch/wire";
 import { render, screen } from "@testing-library/svelte";
 import userEvent from "@testing-library/user-event";
 import { describe, expect, it, vi } from "vitest";
@@ -158,6 +159,61 @@ describe("ChatView", () => {
 		expect(log.children).toHaveLength(0);
 	});
 
+	it("groups batched tool calls (shared stepId) into one DaisyUI list", () => {
+		const chunks: RenderedChunk[] = [
+			{
+				seq: 1,
+				role: "assistant",
+				chunk: {
+					type: "tool-call",
+					toolCallId: "a",
+					toolName: "read_file",
+					input: { path: "/a" },
+					stepId: "t1#0" as StepId,
+				},
+				provisional: false,
+			},
+			{
+				seq: 2,
+				role: "assistant",
+				chunk: {
+					type: "tool-call",
+					toolCallId: "b",
+					toolName: "list_dir",
+					input: { path: "/b" },
+					stepId: "t1#0" as StepId,
+				},
+				provisional: false,
+			},
+			{
+				seq: 3,
+				role: "tool",
+				chunk: {
+					type: "tool-result",
+					toolCallId: "a",
+					toolName: "read_file",
+					content: "contents-of-a",
+					isError: false,
+					stepId: "t1#0" as StepId,
+				},
+				provisional: false,
+			},
+		];
+
+		const { container } = render(ChatView, { props: { chunks } });
+
+		// One DaisyUI list with two rows (one per call), not separate cards.
+		const lists = container.querySelectorAll("ul.list");
+		expect(lists).toHaveLength(1);
+		expect(container.querySelectorAll("ul.list > li.list-row")).toHaveLength(2);
+
+		// Both call names + the available result are shown; the result is absorbed
+		// (no standalone tool-result card).
+		expect(screen.getByText("read_file")).toBeInTheDocument();
+		expect(screen.getByText("list_dir")).toBeInTheDocument();
+		expect(screen.getByText("contents-of-a")).toBeInTheDocument();
+	});
+
 	it("thinking <details> stays open across a streaming update", async () => {
 		const initial: RenderedChunk[] = [
 			{