ci: Add PR workflow timeouts (#13070)
## Why
PR checks should fail sooner when a job hangs or runs unexpectedly long,
reducing wasted CI time and improving feedback loops.
## What
Sets PR-capable GitHub Actions jobs to a 15 minute timeout.
## How
Updated timeout-minutes values in pull_request workflows and added a
missing job-level timeout for JS package change detection. Verified via
pre-push hooks.
