feat(desktop): show live working state on board cards

[loganj]

🤖

Summary

Workstream coordinators need to tell at a glance whether a board card is actively being worked, without opening each channel. This adds a passive live-working indicator to Workstream Board cards: active agents and elapsed working time appear on the matching card, and multiple active agents aggregate together.

This is PR 2 of a four-PR Workstream Board stack, stacked on PR 1. It remains an experiment, off by default; enable Workstream Board in Settings → Experiments to use it.

What changes

• Projects the existing shared active-turn observer state onto discovered board channels; active agents and elapsed time render on the corresponding card.
• Preserves inherited completion and stalled-turn pruning behavior from that shared store.
• Keeps unrelated channels from lighting board cards, and aggregates concurrent active agents on one card.
• Does not add a second subscription, decryption, event-ordering, terminal-handling, or pruning authority.

The implementation lives on this PR branch in activeWorkstreamTurns.ts, WorkstreamBoardScreen.tsx, and WorkstreamWorkingIndicator.tsx.

Related issue

None found. This is an experiment-gated product spike.

Testing

• Exact head 2dfbd23581783c54eba52d405593fb00fdabc0d7:
  • pnpm check
  • pnpm typecheck
  • full Desktop pnpm test: 4,997 passed, 0 failed
• Continuous relay-backed capture exercises absent → active turn starts → elapsed/liveness → completion clears. Its end-to-end assertions also cover concurrent workers, unrelated-channel exclusion, and silent-turn pruning.
• Two independent Royal reviews cleared the rebased exact head with zero findings (content scores: 9.7/10 and 9.5/10).

Acceptance gates

• Board working state is a projection of the existing active-turn observer store.
• Active agents and elapsed time render on matching cards; multiple agents aggregate.
• Completion and stall pruning are inherited; unrelated channels do not light cards.
• Continuous relay-backed demo captured before PR creation.
• Two independent Royal reviews passed at the exact PR head with zero findings.
• Required CI checks are green.
• Maintainer review is complete.

Note

Security may report the known baseline-wide RUSTSEC-2026-0258 / h2 0.4.14 advisory. A separate fix lane owns it; it is unrelated to this Desktop-only diff.

Demo

The qualifying native 36.44-second MP4 is preserved locally and available on request; it is intentionally not uploaded to CloudFront/S3. SHA-256: 6e7fb5bafa8bfe77c9b79c3e763c9aabd330bbf044357598051c8bc81ed5df1b.

Sampled frames from that uninterrupted relay-backed capture:

Before active work	Work starts

Elapsed work	Concurrent workers

Unrelated channel excluded	Completion clears card