test: stop changelog --since test colliding with entry prose

[kome12]

Problem

The Version Packages release PR (#554) is failing CI on the changelog command --since regression test, even though the source change that added it (#572) passed. The failure is a self-collision, not a code regression:

AssertionError: expected '## 1.43.2\n\n### Patch Changes\n\n- […' not to contain 'No changelog entries found'

The test asserts that nansen changelog --since <major.minor> output does not contain the literal string "No changelog entries found" — using the command's no-match sentinel as proof that entries were matched. But #572's own changelog entry documents the fix with the prose …silently returning "No changelog entries found" for a version missing its patch number….

#572 passed because CHANGELOG.md on its branch didn't yet contain that entry — the changesets bot only rolls it into the 1.43.2 section when it generates the Version Packages PR. Once it did, --since 1.43 legitimately returns the 1.43.2 section, whose prose contains the sentinel, and the test trips. This also breaks main the moment #554 merges.

Fix

Assert on structure instead: the newest version's ## x.y. heading must be present in the filtered output. The heading appears only when entries were actually included, and the single-line no-match message has no heading — so it proves the same thing without colliding with entry prose. The toBe(explicitZeroForm) equivalence check (the real regression guard) is unchanged.

Verification

• Reproduced the exact CI failure locally by swapping in the release-branch CHANGELOG.md; confirmed the old assertion fails and the new one passes against it.
• Full suite: 2596 passed / 2 skipped. Lint clean.

Test-only change → no changeset.

🤖 Generated with Claude Code

[nansen-pr-reviewer]

pr-reviewer Summary for #65bc5b8

✅ No issues found

The code review completed successfully with no findings.

Review effort: 1/5 (Trivial)

Summary

This PR fixes a self-collision in the changelog --since regression test: the old not.toContain('No changelog entries found') assertion tripped when a legitimate changelog entry's prose quoted that exact sentinel string.

The replacement — expect(partialForm).toContain(## ${majorMinor}.) — is a sound structural check. A version heading only appears in the output when entries were actually matched; the no-match sentinel is a single line with no heading. The core equivalence guard (toBe(explicitZeroForm)) is untouched. The CHANGELOG regex correctly handles both ## 1.43.1 and ## [1.43.1] heading formats. No changeset is needed or expected for a test-only fix.

No findings — this is a clean, well-reasoned fix.

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Token usage: 16 input, 2,210 output, 194,334 cache read, 17,580 cache write | Usage Guide

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[nansen-pr-reviewer]

Auto-approved

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• It contains only test changes

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