CI: reuse persistent runner caches (npm/gradle/android-sdk volumes)

Node lives in the npm volume, cmdline-tools download is guarded, and
sdkmanager no-ops when packages are present. First run seeds the
volumes; later runs skip all toolchain downloads.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitea/workflows/release.yml

@@ -20,25 +20,33 @@ jobs:
           git fetch -q --depth 1 "https://git.rehbock.xyz/${{ github.repository }}.git" "${{ github.sha }}"
           git checkout -q FETCH_HEAD
 
-      - name: Install Node 22
+      # /root/.npm and /root/.gradle and /root/android-sdk are persistent named
+      # volumes (act_runner config.yaml) — downloads below only happen on a cold cache.
+      - name: Install Node 22 (cached in npm volume)
         run: |
+          NODE_DIR="$HOME/.npm/_node-v22.14.0"
+          if [ ! -x "$NODE_DIR/bin/node" ]; then
             curl -sLo /tmp/node.tar.xz https://nodejs.org/dist/v22.14.0/node-v22.14.0-linux-x64.tar.xz
-          mkdir -p /opt/node && tar xJf /tmp/node.tar.xz -C /opt/node --strip-components=1
-          echo "/opt/node/bin" >> "$GITHUB_PATH"
-          /opt/node/bin/node --version
+            mkdir -p "$NODE_DIR" && tar xJf /tmp/node.tar.xz -C "$NODE_DIR" --strip-components=1
+          fi
+          echo "$NODE_DIR/bin" >> "$GITHUB_PATH"
+          "$NODE_DIR/bin/node" --version
 
       - name: npm ci
         run: npm ci --no-audit --no-fund
 
-      - name: Install Android SDK + NDK
+      - name: Install Android SDK + NDK (cached volume)
         run: |
-          mkdir -p "$HOME/android-sdk/cmdline-tools"
+          SDK="$HOME/android-sdk"
+          SDKMAN="$SDK/cmdline-tools/latest/bin/sdkmanager"
+          if [ ! -x "$SDKMAN" ]; then
+            mkdir -p "$SDK/cmdline-tools"
             curl -sLo /tmp/ct.zip https://dl.google.com/android/repository/commandlinetools-linux-11076708_latest.zip
             unzip -q /tmp/ct.zip -d /tmp
-          mv /tmp/cmdline-tools "$HOME/android-sdk/cmdline-tools/latest"
-          SDKMAN="$HOME/android-sdk/cmdline-tools/latest/bin/sdkmanager"
-          yes | "$SDKMAN" --sdk_root="$HOME/android-sdk" --licenses >/dev/null 2>&1 || true
-          "$SDKMAN" --sdk_root="$HOME/android-sdk" \
+            mv /tmp/cmdline-tools "$SDK/cmdline-tools/latest"
+          fi
+          yes | "$SDKMAN" --sdk_root="$SDK" --licenses >/dev/null 2>&1 || true
+          "$SDKMAN" --sdk_root="$SDK" \
             "platform-tools" "platforms;android-36" "build-tools;36.0.0" \
             "ndk;27.1.12297006" "cmake;3.22.1" >/dev/null