test: lefthook - Verify staging and operation safety #389

Testing / Coverage Summary

Demonstrate safe actual Git operations using disposable repositories and a local bare remote: successful/rejected commits and pushes, partial staging, filenames containing spaces and merge/rebase behaviour. Reuse existing branch-validator coverage; do not duplicate implementation.

Acceptance Criteria

• Valid staged/invalid unstaged and invalid staged/valid unstaged cases covered.
• Index and working-tree contents preserved.
• Intentional failures block relevant operation.
• Merge/rebase behaviour exercised, not inferred from configuration.
• Stubbed failures distinguished from genuine journal/build failures.

Definition of Ready

• Scope, fixtures, prerequisites and overlap identified.

Definition of Done

• Criteria pass; commands, revision, environment and exit codes recorded.
• Documentation reflects tests; 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/milestone.