test(tia): cover monorepo baseline and path regressions

[einar-hansen]

What:

• Bug Fix (regression coverage)
• New Feature

Description:

Add regression coverage for TIA baseline detection and file selection in monorepos. These cases preserve coverage from #1809 alongside the implementation in #1914.

Depends on #1914. This draft targets 5.x and contains tests and output snapshots only. It does not include the implementation from #1914. Keep the draft blocked until that prerequisite merges.

The 26 new cases cover:

• GitHub and GitLab baseline detection from project subdirectories, nested repositories, linked worktrees, and submodules.
• Relative and absolute gitdir and commondir pointers, and malformed nested Git metadata without falling back to the parent remote.
• Separate caches for sibling projects with the same name, and matching cache identity and fingerprints across worktrees.
• Actual Unicode filenames with core.quotePath=true, staged and committed moves outside the project, cosmetic changes, and untracked files.

The Unicode cases use an actual Æ character. PHP leaves the single-quoted \u{26a1} strings in #1914 literal, so those existing fixtures do not exercise non-ASCII filenames.

Validation:

Validated in a temporary checkout combining upstream 83baa5de and #1914 at 85aac6a8, with this PR's tests applied.

• New regression tests with fix(tia): support a Pest project nested in a git repository #1914: 26 passed, 27 assertions.
• Negative control using current upstream implementations without fix(tia): support a Pest project nested in a git repository #1914: 21 failed, 5 passed, confirming the dependency.
• Full composer test: passed, including Rector, Pint, PHPStan, 100% type coverage, unit tests, parallel tests, and integration tests.
• Unit suite: 1,623 passed. Parallel suite: 1,622 passed. Both retain the suite's existing warning, skipped, incomplete, todo, notice, and deprecation fixtures.
• Integration suite: 254 passed, 1 skipped, 758 assertions.

The output snapshots include #1914's tests and the 26 cases added here. The parallel summary changes from 1,581 passed / 3,431 assertions to 1,622 passed / 3,483 assertions. Snapshot regeneration changed only tests/.snapshots/success.txt and the expected summary in tests/Visual/Parallel.php.

The validation checkout uses PHP 8.5.10 and ParaTest 7.26.0. ParaTest 7.26.1 introduces an unrelated upstream WrapperWorker constructor incompatibility. The dependency constraint and application code are unchanged in this PR.

Related:

• Depends on fix(tia): support a Pest project nested in a git repository #1914.
• Carries regression coverage from feat(tia): support projects in git repository subdirectories (monorepos) #1809.