Add execution report heartbeat alerts

[Pigbibi]

Summary

• add an Execution Report Heartbeat workflow that checks recent runtime report JSON instead of Cloud Run request success
• filter reports by platform/service so shared report buckets cannot mask a missing service report
• document setup and behavior in English and Chinese

Validation

• python -m py_compile scripts/execution_report_heartbeat.py
• real read-only GCS smoke with Telegram disabled
• git diff --check

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Match the persisted month directory format

The default heartbeat glob is built with the raw month segment like 2026-06, but the strategy-run writer stores the period through safe_key(run_period), so the actual latest report path is under 2026_06/latest.json. With only FIRSTRADE_GCS_STATE_BUCKET / FIRSTRADE_STATE_PREFIX configured as documented, this glob never matches the persisted strategy-run JSON and the scheduled heartbeat will alert/fail even after a successful run.

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