[codex] Remove associated PR changelog validation

[Oseltamivir]

Summary

• remove the push-only Validate the associated pull request step from test-changelog-gate.yml
• remove the regression test dedicated to that step
• leave the production run-sweep.yml changelog validation unchanged

Reason

The test workflow began validating the full associated PR diff on every relevant branch push. After a stale PR merged current main, this extra check rejected its changelog entry placement even though the workflow’s validator and gating test suite passed. This removes that recently added cross-PR validation from the test workflow.

Impact

Test Changelog Gate continues to run the validator, reuse, gating, and historical fixture tests. Actual sweep runs continue to validate perf-changelog.yaml through run-sweep.yml.

Validation

• gate/reuse pytest suite: 96 passed
• actionlint .github/workflows/test-changelog-gate.yml
• git diff --check

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Note

Low Risk
CI-only change to a test workflow; production sweep changelog gating in run-sweep.yml is explicitly unchanged.

Overview
Removes the Validate the associated pull request step from Test Changelog Gate, so branch pushes no longer run validate_perf_changelog.py against the full open PR diff (base...HEAD) for the commit’s linked PR.

That step was added recently and could fail when a stale PR rebased onto current main—for example rejecting changelog entry placement even when the workflow’s pytest suite and historical fixture checks still passed.

The workflow keeps pytest coverage, historical push validation fixtures, and the unchanged changelog checks in run-sweep.yml. The regression test that asserted the removed step’s perf-changelog.yaml skip behavior is deleted with it.

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[claude]

Claude finished @Oseltamivir's task in 28s —— View job

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Review

• Analyze PR changes
• Post review

LGTM - no blocking issues found. The removal is clean: the workflow step and its dedicated regression test are fully excised with no dangling references or orphaned code.