Sidebar: show a parent thread as working while its child threads work

[lukemaj]

Parent

#25

Outcome

A parent thread's sidebar row shows it is working while any of its child threads works, with the number of working agents.

Acceptance criteria

• A shared helper derives, from thread summaries the client already has, whether a thread or any descendant child thread (fork child threads, Prism jobs) is working, and how many are.
• The parent row shows the existing Working pill and timer with · N agents while any child works, following the same rules as upstream's native subagent fleets (backgroundLiveness), including Active-section placement.
• The pill clears when the last child finishes; a child awaiting approval surfaces on the parent like existing approval states.
• No new websocket payloads, no continuously repainting animation.
• Every upstream-file edit is in scripts/fork-upstream-edits.txt and docs/fork-features.md.

Non-goals

• Mobile (does not hide child threads yet) and the opt-in legacy sidebar.
• Issue status (Computed Issue status, status grouping and filters #29 consumes the helper).

Blocked by

None

Required proof

• Logic tests for the helper: no children, working child, nested child, finished child, child awaiting approval, and the resulting row status.
• Targeted lint and typecheck; scripts/fork-check.sh; independent review of the exact head.

[lukemaj]

Handoff: PR #33 into feat/25-issues, not merged. Head 6c82b456da8626500ccc53babbd9a9f219177911.

What changed:

• New shared helper packages/shared/src/childThreadActivity.ts, childThreadActivityByParent(shells, parentThreadIdOf). It reports working descendant child threads (nested ones included) and any pending approval. Computed Issue status, status grouping and filters #29 can reuse it.
• Sidebar parent row: the existing Working pill and timer, followed by · N agents. A child's approval shows as the parent's Pending Approval. The pill clears when the last child finishes. The fleet precedence is kept, so the parent's own failure still wins.
• Placement: fleets stay in Active because the server's auto-settle sweep skips them. ThreadSettlementReactor now also skips parents whose child threads are working or waiting on approval.

Proof (targeted only):

• packages/shared vp test run src/childThreadActivity.test.ts: 6 passed
• apps/web vp test run src/components/SidebarChildActivity.logic.test.ts: 6 passed
• apps/server vp test run src/orchestration/ThreadSettlementReactor.test.ts, in the host-neutral env from docs/fork.md: 58 passed. The new case fails when the guard is removed. On the raw Mac host, 37 tests in that file fail both with and without this change.
• vp run typecheck in apps/web, apps/server and packages/shared: pass. vp lint on touched files: 0 errors. scripts/fork-check.sh: OK (10 features).

Unverified or out of scope:

• No real-client run.
• The legacy sidebar setting and mobile are unchanged.
• CI has not been checked yet.
• The independent review of this exact head has not been done.

[lukemaj]

Handoff update after independent review: PR #33, not merged. New head 63d5ae2ef18369347f48d1d73812a8c3875706f7.

Review fixes applied:

1. A child waiting on user input now shows the parent's existing Awaiting Input state. The auto-settle guard now keeps a parent active while a child waits on input or has any background work, monitoring included. This matches the parent's own backgroundLiveness != null rule.
2. When the parent is not running, its Working timer starts at the earliest working child. It keeps the parent's own start if the parent's own fleet started earlier. A running parent still times its own turn.
3. · N agents is now rendered outside the aria-hidden timer span, so screen readers hear the count.
4. Legacy sidebar: not wired, as agreed.

Proof:

• packages/shared vp test run src/childThreadActivity.test.ts: 8 passed
• apps/web vp test run src/components/SidebarChildActivity.logic.test.ts: 9 passed
• apps/server vp test run src/orchestration/ThreadSettlementReactor.test.ts, in the host-neutral env from docs/fork.md: 58 passed. The new input and monitoring cases fail when those conditions are dropped from the guard.
• vp run typecheck in apps/web, apps/server and packages/shared: pass. vp lint on touched files: 0 errors. scripts/fork-check.sh: OK.

Unverified: no real-client run, CI not checked, and the fixes have not been re-reviewed at this head.