fix: live sub-agent observability — dispatch cards, steer artifacts, sidebar panel

The pi-style ack protocol (previous commit) left the client describing the
old world: artifact cards read the ack string as a result ("could not be
displayed"), the only job poller rendered on input-available parts that no
longer exist (so wake turns landed invisibly until re-navigation), steers
rendered as learner bubbles with no SVG anywhere, and server-persisted
assistant messages carried empty SDK ids (duplicate React keys).

- persistTurn (turn-service): fill empty message ids at the canonical write
  — server-only messages (last turn's, wake turns') now key uniquely;
  client-authored ids untouched.
- chat.tsx: ONE central /api/jobs poll (fast while jobs run, slow discovery
  cadence, off for job-less sessions) drives every job surface, re-syncs
  once when a job settles (the record already holds the steer + wake
  response at flip time), and adopts server-side wake turns via the same
  turnInFlight machinery as returning mid-turn. Steers branch to the
  artifact card — never a bubble. Composer no longer gates on jobs.
- /api/jobs now reports turnInFlight alongside the job list.
- dispatch-card: the tool-call box — live activity by toolCallId while
  running, quiet "delivered"/"failed" one-liner after; the ack is visible
  observability, the artifact lives in the steer.
- steer-card: renders the delivered artifact by kind (research brief /
  sanitized SVG / sandboxed demo iframe) from the data-subagent-artifact
  part; result renderers extracted and exported from the artifact cards.
- sub-agents-panel: right-sidebar section above the plan tree listing
  running sub-agents (kind, elapsed, live activity) — vanishes when idle.
- tests: dispatch/steer/panel render tests re-target the new protocol;
  persistTurn id-hygiene suite. 229/229 green, build green.

Out-of-lane touches for master review: chat.tsx + components/** (cleared
this wave), app/api/jobs/route.ts, src/server/turn-service.ts, contracts
protocol doc §2. Live-verified on :3003 (full loop, SSR DOM checked).

app/api/jobs/route.ts

@@ -1,10 +1,12 @@
-import { listJobs } from "@/src/server";
+import { isTurnRunning, listJobs } from "@/src/server";
 
 /**
  * Job status polling endpoint (contracts.ts "THE ASYNC PROTOCOL" §4): the
- * client polls GET /api/jobs?chatId=… while any job tool part is pending,
- * finds the job by toolCallId, renders its activity line, and re-syncs the
- * chat when the job flips to done/error.
+ * client's ONE central poller fetches this while any job runs (and slowly
+ * otherwise) to drive the dispatch cards, the sub-agents panel, and the
+ * re-sync when a job settles. `turnInFlight` rides along so the client can
+ * adopt a server-side wake turn (busy state + composer gate) — the same
+ * machinery as returning to a session mid-turn.
  */
 export async function GET(req: Request) {
 	const chatId = new URL(req.url).searchParams.get("chatId");
@@ -14,5 +16,5 @@ export async function GET(req: Request) {
 	if (!/^[A-Za-z0-9_-]+$/.test(chatId)) {
 		return Response.json({ error: "Invalid chatId" }, { status: 400 });
 	}
-	return Response.json({ jobs: listJobs(chatId) });
+	return Response.json({ jobs: listJobs(chatId), turnInFlight: isTurnRunning(chatId) });
 }