feat(supervisor): wide events + warm-start trace propagation

[nicktrn]

Adds wide-event observability for the supervisor: one flat-keyed JSON line per dequeue iteration, workload-server route, and run socket lifecycle event. Events carry trace_id sourced from the inbound W3C traceparent plus meta.run_id and related identifiers, so they join across services by run.

The outbound warm-start POST also forwards the inbound traceparent so the upstream receiver continues the same trace instead of minting a new one.

Off by default behind TRIGGER_WIDE_EVENTS_ENABLED. With the flag off, no events are emitted, no ALS state is allocated, and the outbound warm-start request is unchanged — every call site was audited to confirm the off path is byte-identical to current behavior.

Dequeue-path phase timings recorded under phase.<name>.duration_ms: restore, warm_start, workload_create. A path_taken extra distinguishes restore / warm_start / cold_create / skipped_no_image.

Refs TRI-9480.

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ℹ️ Recent review info

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Reviewing files that changed from the base of the PR and between 570d648 and 671b137.

📒 Files selected for processing (7)

• apps/supervisor/src/env.ts
• apps/supervisor/src/index.ts
• apps/supervisor/src/wideEvents/emit.test.ts
• apps/supervisor/src/wideEvents/emit.ts
• apps/supervisor/src/wideEvents/middleware.ts
• apps/supervisor/src/wideEvents/state.ts
• apps/supervisor/src/workloadServer/index.ts

✅ Files skipped from review due to trivial changes (1)

• apps/supervisor/src/wideEvents/emit.ts

🚧 Files skipped from review as they are similar to previous changes (6)

• apps/supervisor/src/env.ts
• apps/supervisor/src/wideEvents/emit.test.ts
• apps/supervisor/src/wideEvents/state.ts
• apps/supervisor/src/index.ts
• apps/supervisor/src/wideEvents/middleware.ts
• apps/supervisor/src/workloadServer/index.ts

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• GitHub Check: typecheck / typecheck
• GitHub Check: Analyze (javascript-typescript)

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Walkthrough

This PR adds a supervisor-wide "wide events" observability system: new wideEvents/ modules provide types (State/Phase/Error), traceparent parsing, AsyncLocalStorage context, phase timing/recording, JSON serialization (emit) to stdout, lifecycle middleware (runWideEvent/emitOneShot) and helpers (setMeta/setExtra). Tests cover parsing, state creation, recording, emission, and middleware. Environment flags TRIGGER_WIDE_EVENTS_ENABLED and TRIGGER_WIDE_EVENTS_NOISY_ROUTES gate behavior. Supervisor and WorkloadServer are wired to create and emit wide events across the dequeue loop, HTTP routes, and socket lifecycle.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~75 minutes

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The PR description is comprehensive but the required template sections (Checklist, Testing, Changelog, Screenshots) are not filled in according to the repository template.	Complete the required PR template by filling in the checklist items, testing steps, changelog, and any relevant screenshots following the repository's contributing guide.
Docstring Coverage	⚠️ Warning	Docstring coverage is 57.89% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: adding wide-event observability and trace propagation in the supervisor service.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 4 additional findings.