fix(agent-sre): evaluate burn alerts over their declared windows - #4210

Description

ErrorBudget declares 24-hour burn-rate alerts, but firing_alerts() calls burn_rate() with its one-hour default. An error two hours ago appears in the reported 24-hour burn rate while neither alert fires.

Evaluate each alert using its own window_seconds. Thresholds and burn-rate arithmetic remain unchanged.

Validation

The regression fails before the fix, covers a two-hour-old error, and confirms expiration beyond 24 hours. Objective tests: 21 passed. Full package run: 1,495 passed, 3 skipped, 1 known baseline failure (the separate Windows benchmark clock bug).

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.

The Agent-SRE changelog now records that errors from one to 24 hours ago can correctly raise SLO status to WARNING or CRITICAL when the configured alert window includes them. Documentation link and frontmatter checks pass after this addition.

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 independent full package run has no failures: one pre-existing Windows benchmark failure remains, as documented above. Focused tests pass; the combined run with fix(agent-sre): measure benchmark duration with a monotonic clock #4206 passes (1,505 passed, 3 skipped).
• 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.