(MOT-4290) fix: harden worker presence and diagnostics

[ytallo]

Summary

• Reconcile engine and worker-manager state so the Console distinguishes connected, starting, stopped, absent, and unknown workers.
• Show actionable Harness empty states, worker connection status, and trace-stream stall diagnostics.
• Add UI-003, a real Console + Harness + scripted-router Playwright scenario proving the composer remains editable and a persisted queued message drains exactly once during streaming.
• Synchronize UI-003 through the native harness::turn-started, harness::message-queued, and terminal harness::turn-completed triggers; the scripted gate uses an early-release latch, with no status/gate polling or synchronization sleeps.
• Harden Harness startup/config registration retries and E2E port/process diagnostics, with focused retry and occupied-port validation.
• Keep explicitly downloaded skills visible by default, add browser frontend guidance, and refresh stale documentation links.

Context

The recording exposed several misleading states: a running manager process could be shown as a healthy worker without a registered connection, stopped workers could collapse into an empty state without diagnostics, the chat composer could appear unusable during a running turn, and a stalled trace had no actionable feedback.

The backend stop and queued-message scenarios (INT-011/INT-012) are now on main; this branch builds on them with UI-003 through the production Console surface. The worker-manager port collision remains an external runtime/environment issue, so the E2E launcher now fails before boot on an occupied port and reports early child-process exits with log tails.

Lifecycle hooks were intentionally not used as test observers: they are synchronous execution boundaries that can veto or mutate a turn. The async lifecycle trigger types expose the exact facts this scenario needs without inserting test behavior into the production turn path.

Validation

• Console: app/E2E TypeScript checks, Biome, and 15 focused Vitest tests passed.
• Console Playwright UI-003: 3 consecutive real-stack runs passed, plus a focused run with the event-driven latched gate.
• Harness: 306 crate tests and 90 integration harness tests passed; rustfmt and E2E shell syntax passed.
• Integration runner: scripted-router unit tests and clippy with warnings denied passed.
• iii-directory: UI typecheck/build, 261 Rust tests, and 44 BDD scenarios passed.
• Occupied-port fail-fast probe and git diff --check passed.

Fixes MOT-4290

[vercel]

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Project	Deployment	Actions	Updated (UTC)
workers	Ready	Preview	Jul 31, 2026 10:05pm
workers-tech-spec	Ready	Preview	Jul 31, 2026 10:05pm

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[github-actions]

skill-check — worker

0 verified, 51 skipped (no docs/).

Layer	Result
structure	✓
vale	✓
ai	✓
render	✓

Four for four. Nicely done.