docs: warn when catching permanentRedirect (#97496)
## Summary
Document that `permanentRedirect()` throws and should be called outside
a broad `try/catch` block.
The `redirect()` and `notFound()` references already explain this
control-flow requirement. The `permanentRedirect()` reference omits it,
so application error handling can accidentally suppress the redirect.
Align the page with the `redirect()` reference by adding a dedicated
Behavior section for the try/catch guidance and temporary-redirect
cross-link.
## Verification
- Prettier, ESLint, and `git diff --check`
