fix(libvirt): harden failure observability

[Brad-Edwards]

Plain-Language Summary

• Context: Libvirt lifecycle adapters intentionally collapse a small set of expected backend conditions into portable outcomes.
• Problem: Ambiguous native-error matching and unsafe telemetry extraction could turn real failures into successful no-ops or let logging alter control flow.
• Fix: Classify only genuine native errors with operation-specific codes and emit bounded, non-interfering failure metadata.

Summary

Harden libvirt failure telemetry and native error classification so hostile exception and logging behavior cannot alter backend control flow, while preserving retry state for non-absence failures.

Requirement UIDs

• RUN-316

Related Issues

Closes #1173

ADR Impact

• ADR-015
• ADR-036
• ADR-066

Changes

• Bound and sanitize suppressed-failure metadata while making logger and exception inspection non-interfering.
• Centralize operation-specific native libvirt error classification and apply it across deployment and TechVault lifecycle paths.
• Add adversarial regression coverage for native identity, mismatched resource codes, fail-closed deployment, retry state, and stress-test timing.

Test Plan

• Unit tests pass
• Integration tests pass if applicable
• Configured completion command passes
• No coverage regression

Focused libvirt suite: 364 passed, 2 deselected. Full Python unit suite: 7,235 passed, 3 skipped, 4 xfailed. Ground Control completion, policy, and pre-commit gates passed.

Verification

• pytest implementations/python/tests/test_libvirt_failure_observability.py implementations/python/tests/test_libvirt_backend_driver.py: 364 passed, 2 deselected.
• Full Python unit suite: 7,235 passed, 3 skipped, 4 xfailed.
• Ground Control completion, repository policy, pre-commit, and canonical CI verification passed.

Ground Control Checks

• Configured repository policy command passes
• Pre-push code review and test-quality review completed; all findings fixed or dispositioned

Traceability

• IMPLEMENTS: RUN-316 ← implementations/python/packages/raes_backend_libvirt/_observability.py, RUN-316 ← implementations/python/packages/raes_backend_libvirt/drivers/libvirt/_native.py, RUN-316 ← implementations/python/packages/raes_backend_libvirt/drivers/libvirt/deployment.py, RUN-316 ← implementations/python/packages/raes_backend_libvirt/techvault_lifecycle.py
• TESTS: RUN-316 ← implementations/python/tests/test_libvirt_failure_observability.py, RUN-316 ← implementations/python/tests/test_libvirt_backend_driver.py, RUN-316 ← implementations/python/tests/test_participant_concurrent_batch_reservations.py

Issue Tracking

Closes #1173

Checklist

• Code follows the project's coding standards
• Changelog: owned by Release Please (generated from the Conventional Commit PR title; no per-PR fragment)
• Architectural docs updated if stack, package structure, or key behaviors changed

Documentation

Updated: see diff.