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]

Filter by service before capping inspected reports

When CLOUD_RUN_SERVICE_TARGETS_JSON/RUNTIME_HEARTBEAT_REQUIRED_SERVICES points at a shared report bucket, this loop only reads the newest 20 objects globally before applying _payload_matches. If more than 20 newer reports from other services exist in the lookback window, an acceptable report for a required service that is still within the window is never inspected and the workflow alerts/fails as “missing acceptable report” even though the service reported successfully. Keep scanning until all required services are found or apply the limit after service filtering.

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