build: git-hooks - Add journal link validation #392

Build Summary

Integrate existing local journal-link checker into appropriate content-triggered pre-commit validation. Establish capabilities before blocking; do not promise arbitrary route-existence checking.

Acceptance Criteria

• Supported valid links pass; supported invalid cases fail.
• No external-network checks during commits.
• Actual route/fragment limitations documented.
• Validation read-only; unrelated changes preserved.

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.