enrich OTel error conclusion spans with agent_output.json error details

[Copilot]

sendJobConclusionSpan emitted only "agent failure" or "agent timed_out" as span status — no root cause. The structured errors[] array in agent_output.json was already available on disk at conclusion time but never consulted.

Changes

actions/setup/js/send_otlp_span.cjs

• Lazy-reads /tmp/gh-aw/agent_output.json only when isAgentFailure (zero I/O overhead on success/cancel)
• Adds two new span attributes on failure when errors are present:
  • gh-aw.error.count — total error count from agent_output.errors[]
  • gh-aw.error.messages — up to 5 messages joined with |
• Enriches statusMessage with the first error, truncated to 256 chars

// Before
statusMessage: "agent failure"

// After
statusMessage: "agent failure: Rate limit exceeded on claude-3-5-sonnet"
attributes:    gh-aw.error.count=2, gh-aw.error.messages="Rate limit exceeded on claude-3-5-sonnet | Tool call failed"

actions/setup/js/send_otlp_span.test.cjs

• Added GH_AW_AGENT_CONCLUSION to env save/restore in beforeEach/afterEach
• Added 8 tests covering: attribute values, timed_out enrichment, 5-entry cap (with full count), 256-char truncation, missing/empty errors array, and no-op on non-failure conclusions

[pelikhan]

/q fix live sentry access

[Copilot]

Pull request overview

This PR enriches OTLP job conclusion spans with actionable error details by reading structured errors[] from agent_output.json when the agent fails or times out, improving root-cause visibility in traces.

Changes:

• Lazy-read /tmp/gh-aw/agent_output.json only for failure / timed_out conclusions and derive span status message + error attributes from errors[].
• Add span attributes gh-aw.error.count and gh-aw.error.messages (capped to 5 messages), and truncate enriched statusMessage to 256 chars.
• Extend unit tests to cover enrichment behavior and ensure GH_AW_AGENT_CONCLUSION env handling is isolated per test.

Show a summary per file

File	Description
actions/setup/js/send_otlp_span.cjs	Reads agent_output.json on agent failure/timeouts and emits enriched OTLP status/attributes.
actions/setup/js/send_otlp_span.test.cjs	Adds test coverage for the new enrichment logic and stabilizes env save/restore for the new env var.

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• Files reviewed: 2/2 changed files
• Comments generated: 0