[Feat] Record harness reconnect lifecycle as diagnostic breadcrumbs

[daniel-lxs]

PR 3 of the observability plan (rail #140, death certificate #145/#147). Four breadcrumbs on the diagnostic rail, recorded by ReconnectableHarness:

kind	when	details
harness_disconnected	underlying harness lost its event stream	sessionId
harness_restart_requested	deliberate restart (harness-initiated or external)	source, reason, sessionId
harness_reconnected	respawn succeeded	attempt, maxAttempts, sessionId
harness_reconnect_exhausted	gave up after max attempts	maxAttempts, sessionId

Paired with the exit certificate, a process bounce is now fully reconstructable per task: certificate says why the process died, breadcrumbs say what the worker did about it. Deliberate restarts are labeled with their reason, so certificate-less restart breadcrumbs are self-explanatory.

Guarantees

Same discipline as the rest of the rail: recorder injected as an optional dependency, all calls fire-and-forget through the never-throw recorder, zero behavior change to reconnect logic (verified by the existing 11 reconnect tests passing untouched). Events fire only on lifecycle transitions — nothing per-message or per-tool.

Tests

3 new (disconnect→reconnect pair, exhaustion with attempt count, external request with reason). Full run-task + harnesses suites: 431 pass; typecheck / eslint / prettier / knip clean.

Waiting for bot review + Dan before merge.

🤖 Generated with Claude Code

[roomote-roomote]

No code issues found. See task

Reviewed the four reconnect breadcrumbs recorded by ReconnectableHarness (harness_disconnected, harness_restart_requested, harness_reconnected, harness_reconnect_exhausted) and their wiring through create-harness. The recorder is injected as an optional dependency, every call is fire-and-forget through the never-throw recorder, and lifecycle behavior is unchanged. Verified there is no double-recording on the external afterCurrentTurn path, since the concrete OpenCode harness does not implement the optional requestReconnect, so that branch is not taken and restartCurrentHarness runs instead. Breadcrumbs fire only on lifecycle transitions, and the three new tests cover the disconnect→reconnect pair, exhaustion, and external-reason paths.