feat(ci): Gitea flow is build -> test (boot loader test per loader, parallel) -> release; drop upstream build.yml

iso-2-gitea-build.yml now has three jobs. The ISO goes between them as an artifact; the test job runs steamify-cachyos-dev's vmbootloadertest.sh --install for limine, systemd-boot and grub (needs /dev/kvm on the runner, fails at once with a reason without it); the release is only made when every test passed.

AGENTS.md

@@ -118,8 +118,10 @@ Full write-up, with every trap: `steamify-iso-release` in steamify-cachyos-dev.
   release, whose `bundle.yml` needs the secret `ISO_DISPATCH_TOKEN`) names the release: the Steamify version plus
   GitHub's UTC time, `vX.Y.Z-[dev.]YYYY.MM.DD-HHMM`, an **annotated** tag and a release with notes and the direct
   download link. `feat/steamify` makes a `dev.` pre-release, `master` a real one.
-- `.github/workflows/iso-2-gitea-build.yml` (Gitea, `on: push: tags: v*`, skipped on GitHub) builds the ISO for that
-  tag and attaches it to the mirror's release. The tag decides everything: Steamify version (`steamify-prepare.sh`
+- `.github/workflows/iso-2-gitea-build.yml` (Gitea, `on: push: tags: v*`, skipped on GitHub) runs three jobs for that
+  tag: build the ISO, test it (steamify-cachyos-dev's `scripts/vmbootloadertest.sh --install`, one job per boot loader,
+  parallel up to the runner's capacity; needs `/dev/kvm` on the runner and checks out steamify-cachyos-dev `main` and
+  steamify-cachyos at the ISO's version from the mirror), and only when all tests passed attach it to the mirror's release. The tag decides everything: Steamify version (`steamify-prepare.sh`
   takes `STEAMIFY_VERSION`), file name (`STEAMIFY_ISO_VERSION` -> `iso_version` in `profiledef.sh`), label
   (`STEAMIFY_BUILD_STAMP`), boot menu and `/etc/steammachine-iso-build`. The build reads no clock; without a
   tag everything says `local`.
@@ -129,4 +131,4 @@ Full write-up, with every trap: `steamify-iso-release` in steamify-cachyos-dev.
   GitHub doesn't have, and the release with them. GitHub releases can't hold the ISO (2 GB per file).
 - Gitea needs `[repository.release] FILE_MAX_SIZE` above the ISO (413 otherwise) and the runner
   `container: privileged: true` (archiso mounts `/proc`); the workflow's `--privileged` option is ignored.
-- CachyOS's own `Desktop ISO` workflow (`build.yml`) only runs in `CachyOS/CachyOS-Live-ISO`.
+- CachyOS's own `Desktop ISO` workflow (`build.yml`) is removed here; the test job of iso-2-gitea-build.yml replaces it.