add mpv-fourier scaffold (delivery vehicle for dmabuf-modifier-triage iter1)

mpv on ohm is currently stock arch from [extra]. To ship the
vo_dmabuf_wayland plane-semantics fix per
marfrit/dmabuf-modifier-triage#1, we need an mpv-fourier package
following the same fourier-umbrella pattern as kwin-fourier,
qt6-base-fourier, firefox-fourier, libva-v4l2-request-fourier.

This commit lays down:

- arch/mpv-fourier/PKGBUILD pinning upstream mpv 0.41.0 tarball, with
  empty patch slot in prepare(). replaces=mpv. provides=mpv,libmpv.so.
  When iter1 produces the patch, add it to source=()/sha256sums=()
  and uncomment the patch -p1 line.
- arch/mpv-fourier/README.md documenting why + tracker links
- .gitea/workflows/build.yml job mpv-fourier-aarch64 chained after
  libva-v4l2-request-fourier-aarch64 for marfrit.db serialization.
  Same fermi LXC runner, same makepkg → sign → repo-add → rsync flow.

Initial scaffold builds vanilla mpv 0.41.0 with no fourier patches —
once iter1 lands, bump pkgrel and add the patch.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/workflows/build.yml

@@ -592,6 +592,116 @@ jobs:
         if: always()
         run: rm -f /root/repo_pass /root/.ssh/id_ed25519
 
+  # -------------------------------------------------------------------------
+  # mpv-fourier (aarch64 only) — mpv with fourier-umbrella patches.
+  # Patch slot exists for the vo_dmabuf_wayland plane-semantics fix per
+  # marfrit/dmabuf-modifier-triage#1. Initial scaffold builds vanilla
+  # mpv 0.41.0 — bump pkgrel and add patch to source=() when iter1 lands.
+  # -------------------------------------------------------------------------
+  mpv-fourier-aarch64:
+    needs: libva-v4l2-request-fourier-aarch64
+    runs-on: arch-aarch64
+    continue-on-error: true
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: bootstrap runner (idempotent)
+        run: |
+          set -e
+          retry() { for i in 1 2 3; do "$@" && return 0; rc=$?; echo "retry $i (exit=$rc)" >&2; sleep $((i*5)); done; return 1; }
+          retry pacman -Syu --noconfirm --needed base-devel git rsync gnupg openssh sudo
+
+      - name: import signing key
+        env:
+          PRIV: ${{ secrets.MARFRIT_REPO_PRIVATE_KEY }}
+          PASS: ${{ secrets.MARFRIT_REPO_PASSPHRASE }}
+        run: |
+          set -e
+          rm -rf /root/.gnupg /root/repo_pass
+          mkdir -m700 -p /root/.gnupg
+          printf '%s' "$PASS" > /root/repo_pass
+          chmod 600 /root/repo_pass
+          printf '%s\n' "$PRIV" | gpg --batch --import
+          echo "92D5E96D8F63C75E4116AA1FF5C8C4603D0D250C:6:" | gpg --import-ownertrust
+
+      - name: install deploy ssh key
+        env:
+          KEY: ${{ secrets.MARFRIT_REPO_DEPLOY_KEY }}
+        run: |
+          mkdir -m700 -p /root/.ssh
+          printf '%s\n' "$KEY" > /root/.ssh/id_ed25519
+          chmod 600 /root/.ssh/id_ed25519
+          ssh-keyscan -t ed25519 nc.reauktion.de > /root/.ssh/known_hosts 2>/dev/null
+
+      - name: makepkg mpv-fourier
+        run: |
+          set -e
+          rm -rf /tmp/build-mpv
+          cp -r arch/mpv-fourier /tmp/build-mpv
+          chown -R builder:builder /tmp/build-mpv
+          cd /tmp/build-mpv
+          sudo -u builder -H env MAKEFLAGS="-j$(nproc)" \
+            makepkg --nocheck --noconfirm --syncdeps --cleanbuild
+          ls -la *.pkg.tar.* | grep -v "\.sig$"
+
+      - name: sign mpv-fourier
+        run: |
+          set -e
+          cd /tmp/build-mpv
+          for f in *.pkg.tar.xz *.pkg.tar.zst *.pkg.tar.gz; do
+            [ -f "$f" ] || continue
+            gpg --batch --pinentry-mode loopback --passphrase-file /root/repo_pass \
+                --detach-sign --yes -u 92D5E96D8F63C75E4116AA1FF5C8C4603D0D250C "$f"
+          done
+
+      - name: update aarch64 repo db
+        run: |
+          set -e
+          mkdir -p /tmp/arch-stage-mpv
+          cd /tmp/arch-stage-mpv
+          rm -f *
+          for f in marfrit.db.tar.gz marfrit.db.tar.gz.sig marfrit.files.tar.gz marfrit.files.tar.gz.sig; do
+            curl -sSLf "https://packages.reauktion.de/arch/aarch64/$f" -o "$f" || rm -f "$f"
+          done
+          for ext in xz zst gz; do
+            ls /tmp/build-mpv/*.pkg.tar.$ext 2>/dev/null && \
+              mv /tmp/build-mpv/*.pkg.tar.$ext /tmp/build-mpv/*.pkg.tar.$ext.sig .
+          done || true
+          export GNUPGHOME=/root/.gnupg
+          printf 'pinentry-mode loopback\npassphrase-file /root/repo_pass\n' > /root/.gnupg/gpg.conf
+          printf 'allow-loopback-pinentry\n' > /root/.gnupg/gpg-agent.conf
+          gpg-connect-agent reloadagent /bye
+          pkgs=()
+          for ext in xz zst gz; do
+            for f in *.pkg.tar.$ext; do [ -f "$f" ] && pkgs+=("$f"); done
+          done
+          if [ -f marfrit.db.tar.gz ]; then
+            for f in "${pkgs[@]}"; do
+              name=$(echo "$f" | sed -E 's/-[0-9].*//')
+              repo-remove --sign --key 92D5E96D8F63C75E4116AA1FF5C8C4603D0D250C \
+                marfrit.db.tar.gz "$name" 2>/dev/null || true
+            done
+          fi
+          repo-add --new --sign --key 92D5E96D8F63C75E4116AA1FF5C8C4603D0D250C \
+            --verify marfrit.db.tar.gz "${pkgs[@]}"
+          ln -sf marfrit.db.tar.gz        marfrit.db
+          ln -sf marfrit.files.tar.gz     marfrit.files
+          ln -sf marfrit.db.tar.gz.sig    marfrit.db.sig
+          rm -f marfrit.files.sig
+
+      - name: publish to aarch64
+        run: |
+          set -e
+          retry() { for i in 1 2 3; do "$@" && return 0; rc=$?; echo "retry $i (exit=$rc)" >&2; sleep $((i*5)); done; return 1; }
+          cd /tmp/arch-stage-mpv
+          retry rsync -avL --copy-unsafe-links \
+            -e 'ssh -i /root/.ssh/id_ed25519' \
+            ./ mfritsche@nc.reauktion.de:arch/aarch64/
+
+      - name: wipe secrets
+        if: always()
+        run: rm -f /root/repo_pass /root/.ssh/id_ed25519
+
   # -------------------------------------------------------------------------
   # claude-his-agent Debian (Architecture: all) — same dpkg-deb pattern as
   # lmcp-debian; publishes to bookworm + trixie via hertz reprepro.