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).

src/core/contracts.ts

@@ -303,7 +303,10 @@ export interface JobRecord {
  *     sub-agent loop — isolated context, modelFor(role), the
  *     verify-never-one-shot doctrine (headless-tested demos, looked-at SVGs,
  *     sourced briefs) — tracking a live activity line in the job record.
- *     The client polls GET /api/jobs?chatId=… and renders the activity card.
+ *     ONE central client poll of GET /api/jobs?chatId=… (in Chat) drives every
+ *     job surface: the transcript dispatch cards (live activity by
+ *     toolCallId, quiet one-liner after delivery), the sub-agents sidebar
+ *     panel, and the single re-sync when a job settles.
  *
  *  3. On completion the runner builds a STEER MESSAGE (buildSubagentSteer)
  *     and hands it to the wake pipeline (src/server/jobs.ts): a user-role