fix(super-threads): show agent questions instead of raw ask_user JSON

[clintberry]

Summary

When the agent called its ask_user tool, the thread's action log and the task card's live line showed the literal tool call — Ask_user({"question":"What would you like to name the file…"}) — right above the interactive prompt. Those surfaces now read Asked — {question} with a question icon, and once answered, the row pairs the question with the user's answer in the task history.

The fix is two-layer because action rows are persisted and replayed via snapshots: the server now decodes ask_user tool events with the question text as the action arg (readable placeholder fallback — never the args JSON), and the frontend special-cases both new Ask rows and legacy persisted Ask_user rows (parsing the stored JSON defensively, never throwing), so pre-fix history renders clean too. While a question is open the row shows no spinner — the "needs your input" prompt is the waiting affordance, and an unanswered question no longer spins forever in a terminal task's history.

Closes the last display path of the no-raw-JSON guarantee from docs/brainstorms/2026-06-08-interactive-agent-questions-requirements.md (R9); plan: docs/plans/2026-06-10-001-fix-ask-user-action-row-rendering-plan.md.

Test plan

• Go decoder cases: question extraction, kind/options stripped, JSON-ish question text passes through verbatim, missing/non-string question degrades to the placeholder, generic tools keep the compact-JSON fallback.
• Vitest specs for the display helper: legacy JSON parse, truncated/garbled args, missing arg (synthesized rows), non-question tools untouched.
• go test ./..., vitest run (80/80), tsc -b --noEmit, npm run lint all clean.

Post-Deploy Monitoring & Validation

Display-only change — no schema, API, or agent-runtime behavior touched.

• Validate: in a live session, give deuce a task that makes it ask a question. The action row should read "Asked — {question}" while the prompt is up; answering should pair question and answer in the collapsed history. Open an older session containing pre-fix ask rows and confirm no raw Ask_user({...}) text renders.
• Failure signal: any literal Ask_user({ text visible in a thread, or a blank "Asked —" row.
• Mitigation: revert this PR — display-only, no data migration to unwind.
• Window/owner: next few agent sessions; whoever deploys.

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