feat(wire,kernel,conversation-store): step grouping via stepId for batched tool calls

Expose a per-step grouping key so a client can render a model's batched/parallel
tool calls (those emitted in one step) as one unit, on both the live stream and
replayed history. Key = branded StepId, derived turnId#stepIndex (0-based).

- [email protected]: required stepId on Turn{Tool,ToolResult}Event; optional stepId on
  Tool{Call,Result}Chunk (generation provenance on the chunk, not the StoredChunk
  envelope — StoredChunk unchanged). [email protected] (re-export bump).
- kernel-runtime: mint stepId per step; stamp on tool chunks + tool events.
- conversation-store: chunk-carried stepId round-trips append/load/loadSince for
  free; reconcile copies it onto synthesized (interrupted) results.
- cli: stepId added to event test fixtures (renderer unchanged).

typecheck clean; 509 vitest + 89 bun; biome 0/0. FE courier reply + reference
snapshots regenerated in ../dispatch-web.

1 files changed, 4 insertions, 0 deletions

diff --git a/packages/cli/src/render.test.ts b/packages/cli/src/render.test.ts
index bfdb791..c638584 100644
--- a/packages/cli/src/render.test.ts
+++ b/packages/cli/src/render.test.ts
@@ -1,4 +1,5 @@
 import type { AgentEvent } from "@dispatch/transport-contract";
+import type { StepId } from "@dispatch/wire";
 import { describe, expect, it } from "vitest";
 import { renderEvent } from "./render.js";
 
@@ -41,6 +42,7 @@ describe("renderEvent", () => {
 			type: "tool-call",
 			conversationId: "c",
 			turnId: "t",
+			stepId: "t1#0" as StepId,
 			toolCallId: "tc1",
 			toolName: "read_file",
 			input: { path: "/foo" },
@@ -67,6 +69,7 @@ describe("renderEvent", () => {
 			type: "tool-result",
 			conversationId: "c",
 			turnId: "t",
+			stepId: "t1#0" as StepId,
 			toolCallId: "tc1",
 			toolName: "read_file",
 			content: "file contents",
@@ -82,6 +85,7 @@ describe("renderEvent", () => {
 			type: "tool-result",
 			conversationId: "c",
 			turnId: "t",
+			stepId: "t1#0" as StepId,
 			toolCallId: "tc1",
 			toolName: "read_file",
 			content: "not found",