arch/ffmpeg-v4l2-request-git: FFmpeg 8.1 + V4L2-Request hwaccel for Fourier

First carrier package for the Fourier umbrella. Tracks Kwiboo's
v4l2-request-n8.1 branch (ffmpeg 8.1 base) pinned at commit b57fbbe —
bump _commit to rebase onto newer tip. CI job chained after
claude-his-any so it serializes on the shared aarch64 repo-db;
continue-on-error: true so long ffmpeg builds don't block the debian
downstream.

Deliberately diverges from the AUR package:

- AUR pins 6.1.1 with epoch=2 → would downgrade stock Arch ffmpeg 2:8.1-3.
  We track 8.1 so install is a sideways swap, not a regression.
- AUR pulls X11/AMF/CUDA/FireWire/AviSynth/OpenMPT/Bluray/OpenMAX/JPEG-XL/
  Theora/XVid/rsvg/soxr/ssh/vidstab/modplug/SDL2/Vulkan/JACK/GSM/Speex —
  dropped here; none are needed on a Wayland ARM video-decode fleet.
- AUR uses #branch=…, sha256sums=(SKIP) → every build is tip-of-branch,
  not reproducible. We pin via #commit=<sha>.

Kept: encoders (libx264/libx265/libvpx/libdav1d), VAAPI, libdrm, libv4l2,
neon, OpenGL, PulseAudio, subtitle/font stack, gnutls TLS. SDL2 dropped
means no ffplay binary (mpv covers interactive playback).

provides=(ffmpeg) conflicts=(ffmpeg) so it replaces stock ffmpeg on the
target host deliberately. Primary consumers: ohm (Fourier step 5),
fresnel, ampere.

.gitea/workflows/build.yml

@@ -371,6 +371,117 @@ jobs:
         if: always()
         run: rm -f /root/repo_pass /root/.ssh/id_ed25519
 
+  # -------------------------------------------------------------------------
+  # ffmpeg-v4l2-request-git (aarch64 only) — FFmpeg with V4L2 Request API
+  # hwaccel for Rockchip / Allwinner stateless decoders. Used by the Fourier
+  # umbrella (ohm, fresnel, ampere). Long-running build, so failures don't
+  # block downstream debian jobs.
+  # -------------------------------------------------------------------------
+  ffmpeg-v4l2-request-aarch64:
+    needs: claude-his-any
+    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 nasm
+
+      - 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 ffmpeg-v4l2-request-git
+        run: |
+          set -e
+          rm -rf /tmp/build-ffmpeg-v4l2
+          cp -r arch/ffmpeg-v4l2-request-git /tmp/build-ffmpeg-v4l2
+          chown -R builder:builder /tmp/build-ffmpeg-v4l2
+          cd /tmp/build-ffmpeg-v4l2
+          # Parallelise: fermi has 4 A55 cores; -j4 fits RAM during link.
+          sudo -u builder -H env MAKEFLAGS="-j$(nproc)" \
+            makepkg --nocheck --noconfirm --syncdeps --cleanbuild
+          ls -la *.pkg.tar.* | grep -v "\.sig$"
+
+      - name: sign ffmpeg-v4l2-request-git
+        run: |
+          set -e
+          cd /tmp/build-ffmpeg-v4l2
+          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-ffmpeg
+          cd /tmp/arch-stage-ffmpeg
+          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 "$f"
+          done
+          for ext in xz zst gz; do
+            ls /tmp/build-ffmpeg-v4l2/*.pkg.tar.$ext 2>/dev/null && \
+              mv /tmp/build-ffmpeg-v4l2/*.pkg.tar.$ext /tmp/build-ffmpeg-v4l2/*.pkg.tar.$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-ffmpeg
+          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.