ci: swap artifact upload+download to the mirrored actions (issue 2270)

android.yml and release.yml uploaded via actions/upload-artifact@v3, which
reports success while Gitea stores the result in a format its v4-only
artifact API will never serve back — 72 artifacts on this repo are on disk,
have valid DB rows, and are invisible to every retrieval path. Green jobs
producing nothing retrievable.

release.yml is a producer/consumer pair: android-release uploads
minstrel-apk and image-release downloads it to bundle into the container.
Swapping only the upload would have left download-artifact@v3 reading the
v1/v3 listing and finding nothing, so mirror the download side too —
bvandeusen/download-artifact, pull mirror of forgejo/download-artifact,
pinned at its v5 tag to match the upload pin's major.

Not actions/{upload,download}-artifact@v4: isGhes() throws on the hostname
before opening a connection, so no server-side change reaches it.

Upload steps also set if-no-files-found: error — image-release hard-depends
on minstrel-apk existing, so an empty upload must fail where it happens.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitea/workflows/release.yml

@@ -131,12 +131,19 @@ jobs:
             -PMINSTREL_VERSION_CODE=${{ steps.ver.outputs.code }}
 
       - name: Upload APK as workflow artifact
-        # @v3 because Gitea Actions emulates GHES and the v2 artifact
-        # backend used by upload-artifact@v4 errors with GHESNotSupportedError.
-        uses: actions/upload-artifact@v3
+        # Mirrored action, never actions/upload-artifact — @v4+ refuses on the
+        # hostname, @v3 uploads something Gitea will never serve back. This is
+        # the producing half of a pair: image-release downloads `minstrel-apk`
+        # below with the matching download-artifact mirror. Both must stay on
+        # the v4 protocol — mixing a v3 upload with a v4 download (or the
+        # reverse) yields an empty listing, not an error. See Scribe 2255 / 2270.
+        uses: https://git.fabledsword.com/bvandeusen/upload-artifact@cb8afe72b42edc798abfb8fcb556cf660d894245
         with:
           name: minstrel-apk
           path: android/app/build/outputs/apk/release/app-release.apk
+          # error, not the default warn: image-release hard-depends on this
+          # artifact existing, so an empty upload must fail here, not there.
+          if-no-files-found: error
 
       - name: Attach APK to gitea Release
         shell: bash
@@ -238,7 +245,14 @@ jobs:
         # Tag pushes only — android-release just produced this. Non-tag
         # builds take the "Bundle latest release APK" path below instead.
         if: steps.guard.outputs.ready == 'true' && startsWith(github.ref, 'refs/tags/v')
-        uses: actions/download-artifact@v3
+        # Consuming half of the pair — must match the upload's protocol, so it
+        # uses the download mirror, never actions/download-artifact. Same fork,
+        # same reason: upstream's client-side GHES check rejects this hostname
+        # before it connects. bvandeusen/download-artifact mirrors
+        # code.forgejo.org/forgejo/download-artifact; SHA below is its `v5` tag,
+        # the major matching the upload pin. Pinned, not tagged — the mirror
+        # auto-syncs every 8h and a moved tag would change what runs.
+        uses: https://git.fabledsword.com/bvandeusen/download-artifact@1314311ddb542af343a82d478ac786ceada4143a
         with:
           name: minstrel-apk
           path: client/