test: lefthook - Verify installation and rollback #388

Testing / Coverage Summary

Provide repeatable installation, recovery and removal tests in isolated fixtures: normal installation, disabled lifecycle scripts, manual recovery, non-Git installation, uninstall and reinstall.

Acceptance Criteria

• Each scenario records expected and actual exit codes.
• Removal uses installed executable before dependency removal.
• Dependency removal and hook contents checked without network resolution.
• Unrelated hooks and user changes preserved.
• Fixtures clean up safely.

Definition of Ready

• Scope, fixtures, prerequisites and existing-work overlap identified.

Definition of Done

• Scoped criteria pass; commands, revision, environment and exit codes recorded.
• Documentation reflects tested behaviour; applicable review/checks pass.

Branch instructions

Recheck repository instructions, active work and PR template; independently reviewable branch from develop, no automatic merged-branch reuse. Preserve unrelated changes; no force-push, merge or deployment. Estimate unset; no dates or milestone.