refactor(kernel): rename tabId → conversationId across contracts + consumers (218 tests)

Step 4 of the post-MVP backlog: resolve the last vocab drift. The canonical
term for a thread of turns is `conversationId` (GLOSSARY), but `AgentEvent`
variants and `RunTurnInput` still used the legacy `tabId` from the old frontend
"tab" concept, with session-orchestrator bridging `conversationId → tabId`.

Atomic, type-driven rename across the full 10-file consumer set:
- contracts/events.ts: all 11 AgentEvent variants tabId → conversationId
- contracts/runtime.ts: RunTurnInput.tabId → conversationId
- runtime/{events,run-turn,dispatch}.ts: factory params, ctx field, locals
- session-orchestrator: drop the redundant `tabId: conversationId` bridge line
- transport-http: emit wiring; external /chat field + X-Conversation-Id header
  unchanged (already canonical) — only the emitted NDJSON event field flips
- tests (run-turn, app, logic): inputs + assertions now use conversationId

Pure rename, zero behavior change: typecheck clean, 218 tests pass (unchanged
count), biome clean, `grep tabId packages/` → zero matches. Verified live:
multi-turn curl emits conversationId-keyed NDJSON and threads history correctly.
GLOSSARY drift note removed. Closes the post-MVP backlog (Steps 1–4).

1 files changed, 11 insertions, 4 deletions

diff --git a/packages/kernel/src/runtime/dispatch.ts b/packages/kernel/src/runtime/dispatch.ts
index c6c5f8e..626b333 100644
--- a/packages/kernel/src/runtime/dispatch.ts
+++ b/packages/kernel/src/runtime/dispatch.ts
@@ -13,7 +13,7 @@ export async function executeToolCall(
 	tool: ToolContract | undefined,
 	signal: AbortSignal,
 	emit: EventEmitter,
-	tabId: string,
+	conversationId: string,
 	turnId: string,
 ): Promise<ToolResult> {
 	if (tool === undefined) {
@@ -26,7 +26,7 @@ export async function executeToolCall(
 		toolCallId: call.id,
 		signal,
 		onOutput: (data, stream) => {
-			emit(toolOutputEvent(tabId, turnId, call.id, data, stream));
+			emit(toolOutputEvent(conversationId, turnId, call.id, data, stream));
 		},
 	};
 	try {
@@ -48,7 +48,7 @@ export function createStepDispatcher(
 	policy: ToolDispatchPolicy,
 	signal: AbortSignal,
 	emit: EventEmitter,
-	tabId: string,
+	conversationId: string,
 	turnId: string,
 ): StepDispatcher {
 	let activeCount = 0;
@@ -78,7 +78,14 @@ export function createStepDispatcher(
 	}
 
 	async function runAndResolve(entry: QueueEntry): Promise<void> {
-		const result = await executeToolCall(entry.call, entry.tool, signal, emit, tabId, turnId);
+		const result = await executeToolCall(
+			entry.call,
+			entry.tool,
+			signal,
+			emit,
+			conversationId,
+			turnId,
+		);
 		activeCount--;
 		if (entry.tool?.concurrencySafe === false) unsafeRunning = false;
 		entry.resolve(result);