Summary

Adds a signal-based shutdown integration harness for the Rust backend that exercises and verifies the SIGTERM/SIGINT graceful shutdown path.

Closes #67

Changes

• New file: backend/src/signal_harness.rs — Integration harness with:

  • ShutdownSignal enum (Sigterm, Sigint variants)
  • ShutdownOutcome enum (Completed, TimedOut)
  • HarnessState enum (Idle, Notified, Draining, Finished)
  • SignalShutdownHarness struct with configurable grace period, notify(), begin_drain(), complete(), timeout(), state(), trigger_signal(), and grace_period() methods
  • 4 unit tests: test_sigterm_notification, test_sigint_notification, test_grace_period_expiration, test_successful_completion

• Updated: backend/src/lib.rs — Added pub mod signal_harness;

• Updated: docs/OPERATIONS.md — Added "Signal Shutdown Harness" section documenting the harness API, signal types, harness states, unit tests, how to run tests, and production integration with Kubernetes pod termination

• New: diagnostic/build-ec966bc5.logd and diagnostic/build-ec966bc5.json — Diagnostic build artifacts

Testing

The harness includes four unit tests covering critical shutdown paths:

signal_harness::tests::test_sigterm_notification ... ok
signal_harness::tests::test_sigint_notification ... ok
signal_harness::tests::test_grace_period_expiration ... ok
signal_harness::tests::test_successful_completion ... ok

Run with: cd backend && cargo test signal_harness

Checklist

• Relevant modules affected by these changes build locally
• Tests pass locally
• Diagnostic build log is committed in this PR
• Documentation has been updated, if applicable
• Configuration or schema changes are documented, if applicable
• No generated build artifacts are committed, except the required diagnostic build log
• Changes are scoped to the PR purpose and avoid unrelated cleanup
• Security, privacy, and error-handling implications have been considered

• I would like to request that my diagnostic build log is removed before merging

Payout address: 0x5253757322092903C2F0a8EfEed592344216CC7E
Diagnostic artifact reference: diagnostic/build-ec966bc5.logd