Trim the Godot template cache and separate CI cache keys

Cache only Linux/Windows/macOS/Web release templates instead of the full 1.2 GB
archive, and use distinct binary cache keys for the checks and build jobs so
concurrent runs do not fight over the same cache entry.

docs/RELEASING.md

@@ -63,10 +63,11 @@ setup, so do not rely on it.
 > artifacts. If CI publishing fails again, run
 > `./tools/publish_release.sh <version>` from a checkout with `~/.git-credentials`.
 
-> **Godot cache:** the workflow uses Gitea Actions cache for the Godot binary and the
-> 4.7.2 export templates. The first run still downloads them; subsequent runs restore
-> from cache. If the host cache service is unavailable, remove the cache steps and
-> let the install steps download fresh copies.
+> **Godot cache:** the workflow uses Gitea Actions cache for the Godot binary and a
+> trimmed 4.7.2 export-template set (Linux/Windows/macOS/Web release files only, not
+> Android/iOS). The first run still downloads them; subsequent runs restore from cache.
+> If the host cache service is unavailable, remove the cache steps and let the install
+> steps download fresh copies.
 
 > The workflow lives in `.gitea/workflows/` (Gitea's canonical path). The old
 > `.github/workflows/ci.yml` was removed to avoid double runs on hosts that scan