[Linuxuser67]

Measured on the alpha.13 release build (~7.5 min: setup/apt ~2, SDK ~1, flatpak build ~5.5, bundle ~0.5):

• concurrency cancel-in-progress on PR runs only (ci + flatpak-test): rapid pushes no longer queue full duplicate builds. Main pushes, manual dispatches and release builds never cancel.
• Cache the GNOME SDK/Platform layer (~/.local/share/flatpak + ~/.cache/flatpak, keyed by manifest incl. runtime-version) in the shared flatpak build chain and the tarball job; tarball also caches the cargo registry (keyed by Cargo.lock). Builds stay force-clean/pristine — only downloads are cached. Release provenance unchanged.
• Split cargo fmt into its own dependency-free ubuntu job (~1 min signal) instead of riding the Fedora container job.

Deliberately untouched: the 5.5 min dep recompile (would fight the force-clean doctrine), retention, timeouts, path filters, release triggers.