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, 2 insertions, 1 deletions

diff --git a/src/features/chat/index.ts b/src/features/chat/index.ts
index f1e8e29..4f2091a 100644
--- a/src/features/chat/index.ts
+++ b/src/features/chat/index.ts
@@ -1,4 +1,5 @@
-export type { RenderedChunk } from "../../core/chunks";
+export type { RenderedChunk, RenderGroup, ToolBatchEntry } from "../../core/chunks";
+export { groupRenderedChunks } from "../../core/chunks";
 export type { ChatTransport, HistorySync } from "./ports";
 export type { ChatStore, ChatStoreDependencies } from "./store.svelte";
 export { createChatStore } from "./store.svelte";