fix(agent-sre): measure benchmark duration with a monotonic clock - #4206

Description

BenchmarkRunner measures elapsed duration using the wall clock. The existing test_latency_tracked fails on unchanged main under Windows because fast calls report zero duration; wall-clock adjustments can also distort timeout classification.

Use time.perf_counter() for duration measurements in both success and exception paths. Report timestamps continue using the wall clock.

Validation

Two deterministic cases cover a frozen wall clock, a successful call exceeding its timeout, and an exception. Both duration cases fail before the fix. Benchmark tests: 25 passed. Full package suite: 1,497 passed, 3 skipped.

All regressions were reproduced on origin/main 406ddd4d before the production change. Whitespace checks pass. Ruff passes on the changed files. Changed-line spelling passes with the existing API identifier Deduplicator allowed in the temporary check input.

Scope: the existing Agent-SRE source tree, which remains exercised by repository CI. Combined validation of these six independent SRE fixes: 1,505 passed, 3 skipped on Windows/Python 3.12.

Type of Change

• Bug fix (non-breaking correction of existing behavior)

Package(s) Affected

• agent-sre

Checklist

• Changed code follows the project style checks; the exact validation scope is recorded above.
• Regression tests or existing package tests verify the change, as detailed above.
• The relevant test suites passed; commands, scope, and skips are recorded above.
• Documentation is updated where needed; the behavior and compatibility implications are described above.
• The Microsoft CLA check has passed for this contribution.

Attribution & Prior Art

• Related prior contributions are credited below; this PR introduces no unattributed code from external projects.
• External design influences, where applicable, are identified below.

Prior art / related projects: Uses the existing Agent-SRE implementation and standard library operations. No code was copied or adapted from an external project.

AI Assistance

I reviewed the specific changes in this diff before this PR was opened.

Codex assisted with implementation, regression tests, and local validation under my direction.

• I reviewed this diff before submission; its behavior, rationale, and tradeoffs are documented above.
• Tests and verification appropriate to this change were run, with limitations disclosed above.
• Submission followed my direction and my review of these specific changes.
• No AI-generated reviews of other contributors' PRs were posted as part of this contribution.

IP, Patents, and Licensing

• This change uses the existing project implementation and ordinary software techniques; no proprietary or patent-specific technique is introduced.
• Understanding or using this change requires no NDA or separate licensing agreement.
• This contribution remains under the repository's MIT License and introduces no third-party source code or additional license terms.

Related Issues

Newly reproduced defect; the reproduction and regression coverage are described above.