feat: emit enriched agent-core trace events

[Svaag]

Summary

• bump agent-core to v0.5.0 for observatory trace correlation fields
• verify Engineering Loop trace emission includes graph-node traceback events and change/PR/workflow correlation

Validation

• uv run --group dev mypy src
• uv run --group dev pytest -q

[chatgpt-codex-connector]

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Reviewed commit: be88e0c376

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[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 35cf9e71b1

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• Open a pull request for review
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• Comment "@codex review".

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[Svaag]

Addressed the remaining Codex review in 3d71445: publish paths now call emit_published_trace(...) after pr_results is available (CLI PR command, operator harness, and daemon publish flow), and a regression test covers re-emitting from the real pr_results[].github_pr / pr_results[].commit shape. CI is green.