Fix Jaah Deploy platform bundles timeout

The Jaah Deploy workflow (.github/workflows/jaah-deploy.yml) fails on develop because its "platform bundles" job times out. The step "Build + import-smoke the darwin-arm64 and windows-x64 bundles" hits its 30-minute limit while fetching vendor runtime artifacts. For example, `fetch codex/windows-x64: 162230206 bytes in 459.8s` (run 41362531844, job 125016727121, 2026-11-01). The same failure ended run 41358109461 for merge 04a792568d. `apply (dev)` succeeded in both runs, so dev did deploy, but every run ends red and the platform bundles are not published. Ask: - Make the platform-bundles step reliable. Options: cache the fetched artifacts between runs, fetch in parallel, or raise the step timeout with a justified bound. - Make a slow fetch fail fast with a named cause instead of a silent 30-minute timeout. Out of scope: changing which artifacts are bundled; the apply job. Done means: - Two consecutive Jaah Deploy runs on develop finish with `platform bundles` = success.

Platform-bundle pins now fetch 8-parallel under a named 20-min budget and are cached via actions/cache. Two consecutive develop deploys (41371509962, 41373139130) had platform bundles = success. Follow-up #7684 fixed a cache-path mismatch; its first warm hit isn't observed yet. Quick gate green. Memory: none applied.