test: git-hooks - Add unit test validation #396

Testing / Coverage Summary

Add reliable non-watch unit-test validation before pushes.

Acceptance Criteria

• Existing unit-test command used, not aggregate command repeating build/E2E.
• Passing tests permit pushes; failures reject them.
• No browser installation required.
• Discovery and supported file types documented.
• Existing test-configuration work reused, not duplicated.

Definition of Ready

• Scope, fixtures, prerequisites and overlap identified.

Definition of Done

• 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 before implementation; independently reviewable branch from develop, no automatic merged-branch reuse. Preserve unrelated changes; no force-push, merge or deployment. Estimate unset; no dates/milestone.