Summary

Improve the regression test suite around worktree command flows before larger code refactors.

What Changed

• added create-flow regression coverage for tag-based worktree creation and switch file output
• added config discovery regression coverage for bare and linked worktree contexts
• replaced several low-signal unit tests with higher-signal command contract tests for switch, rename, and delete
• made new command tests use unique worktree names so they remain stable in full-suite runs
• removed placeholder utils tests that were not asserting behavior

Why

The existing suite had good breadth, but some tests were mostly checking trivial string properties while key command entry points were still lightly protected. This change strengthens the safety net so upcoming refactors can rely on behavior-focused coverage.

Impact

• improves confidence when refactoring command-layer code
• reduces false confidence from low-value tests
• keeps the full suite green while adding stronger command regressions

Validation

• cargo test --all-features -- --test-threads=1