feat(web): retain finished subagents across hydration

[chuks-qua]

What

Keep settled delegated work inspectable in the Subagents panel after completion, thread switching, and hydration.

Why

Finished subagents disappeared when volatile narrative state settled. This completes the second tracer-bullet slice of #916 and unblocks #919.

Key Changes

• Reconcile live and hydrated subagent records by stable tool-call identity.
• Show completed, failed, and cancelled work in a dedicated Finished roster with status, result, elapsed duration, and terminal-time ordering.
• Persist lifecycle timestamps through narrative settlement and repository hydration.
• Keep Active or Finished selection per thread and clear it when a thread is deleted.
• Add focused server, projection, store, and component coverage.

Verification

• Live Browser: observed one delegated row move from Active to Finished with a 20-second duration and its result.
• Live Browser: switched to another thread and observed an empty Finished roster, then returned to the original row.
• Live Browser: reloaded the app and observed the Finished tab, completed status, duration, task, and result restored from persistence.
• Focused tests: 122 passed across the affected server and web suites.
• bun run verify: passed all typecheck, lint, unit-test, and agent-script gates.

Visual Evidence

Active roster before settlement:

Finished roster after settlement:

Thread isolation with an empty Finished roster:

Hydrated restoration after a full reload:

Closes #918

[coderabbitai]

📝 Walkthrough

Walkthrough

Tool-call lifecycle timestamps are now persisted during narrative storage. The web Subagents roster reconciles live calls with hydrated records into active and finished rows, renders terminal statuses, and remembers the selected roster tab independently for each thread.

Changes

Subagent lifecycle and roster

Layer / File(s)	Summary
Persist tool-call lifecycle timestamps apps/server/src/repositories/tool-call-record-repo.ts, apps/server/src/services/narrative-store.ts, apps/server/src/**/__tests__/*	Repository inputs preserve explicit startedAt and completedAt values, while NarrativeStore records completion and settlement timestamps. Tests verify persisted timestamps and durations.
Reconcile active and finished subagents apps/web/src/components/subagents/subagent-projection.ts, apps/web/src/components/subagents/__tests__/*	projectSubagents merges live calls with hydrated narrative records, derives terminal status and timing, removes duplicates, and sorts active and finished rows deterministically.
Render roster views and persist tab selection apps/web/src/components/panels/SubagentsPanel.tsx, apps/web/src/stores/diffStore.ts, apps/web/src/components/panels/__tests__/*, apps/web/src/__tests__/diffStore.test.ts	The panel renders finished statuses and separate empty states, while the store remembers each thread’s selected tab and clears it with the thread.

Estimated code review effort: 4 (Complex) | ~45 minutes

Possibly related issues

• feat: redesign subagent activity and add a right-panel workspace #916 — Covers the active/finished roster redesign and lifecycle timestamp requirements implemented here.
• feat: show active subagents in the right panel #917 — Covers the projection, panel, hydration reconciliation, and tab-state work updated in this PR.

Possibly related PRs

• Mzeey-Empire/mcode#902 — Directly relates to persisted tool-call lifecycle timestamps used for duration and hydration.
• Mzeey-Empire/mcode#921 — Modifies the Subagents roster and projection flow that this PR refactors.

Poem

A rabbit watched timestamps bloom,
While agents hopped from active room.
Finished rows wore badges bright,
Tabs remembered threads just right.
Hydrated tales kept every trace—
“Well done!” twitched one whiskered face.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 21.05% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The changes satisfy #918 by adding finished-state hydration, terminal statuses, sorting, deduplication, tab restoration, and coverage.
Out of Scope Changes check	✅ Passed	The diff stays focused on subagent hydration, persistence, UI, and tests, with no clearly unrelated changes.
Title check	✅ Passed	The title is concise and clearly summarizes the main change: retaining finished subagents across hydration.
Description check	✅ Passed	The description covers What, Why, Key Changes, verification, and evidence, so it is mostly complete for the template.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

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