test: git-hooks - Verify journal validation #391

Testing / Coverage Summary

Verify current journal gate without generating exports.

Acceptance Criteria

• Valid content passes; schema-invalid content blocks commits.
• Applicable required fields, duplicate slugs and README exclusions tested.
• Whole-directory interactions demonstrated and documented.
• No journal:parse, export writes or auto-staging.
• Existing journal commands remain functional.

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.