Triggered by the typed-router.d.ts regeneration in 3198698. Documents
three approaches (lefthook pre-commit, gitignore+postinstall, CI-check)
with their trade-offs. Defers selection to implementation time;
recommends bundling with the next pages-tree refactor (likely WS-3 PR-B).
Co-Authored-By: Claude <noreply@anthropic.com>