Add Android APK release workflow

Bubblewrap TWA config for chat.sune, plus a manually dispatched workflow
that builds, signs, verifies against assetlinks.json, attests provenance
and publishes the release for the tag given as input.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.github/workflows/apk.yml

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+name: Release APK
+run-name: Release APK ${{ inputs.version }}
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'Release tag to create, e.g. v1.0.0'
+        required: true
+        type: string
+
+concurrency: release-apk
+
+permissions: {}
+
+jobs:
+  apk:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    permissions:
+      contents: write # create the tag + release
+      id-token: write # sign the build attestation
+      attestations: write
+    env:
+      TAG: ${{ inputs.version }}
+    steps:
+      - name: Validate version
+        run: |
+          [[ "$TAG" =~ ^v([0-9]+)\.([0-9]+)\.([0-9]+)$ ]] || { echo "::error::version must look like v1.0.0"; exit 1; }
+          MA=${BASH_REMATCH[1]} MI=${BASH_REMATCH[2]} PA=${BASH_REMATCH[3]}
+          (( MI < 100 && PA < 100 )) || { echo "::error::minor and patch must be < 100"; exit 1; }
+          echo "VERSION=${TAG#v}" >> $GITHUB_ENV
+          echo "CODE=$((MA*10000 + MI*100 + PA))" >> $GITHUB_ENV
+          echo "APK=sune-$TAG.apk" >> $GITHUB_ENV
+          echo "BT=$RUNNER_TEMP/sdk/build-tools/36.1.0" >> $GITHUB_ENV
+
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+
+      - name: Fail if the release already exists
+        if: github.ref == 'refs/heads/master'
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          if gh release view "$TAG" --repo "$GITHUB_REPOSITORY" >/dev/null 2>&1; then
+            echo "::error::$TAG already exists"; exit 1
+          fi
+
+      - uses: actions/setup-java@de7274f081f381c8f8158605e0321c36c376e2e6 # v6.0.1
+        with:
+          distribution: temurin
+          java-version: 17
+
+      - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
+        with:
+          node-version: 22
+
+      - name: Install Android SDK + Bubblewrap
+        run: |
+          SDK=$RUNNER_TEMP/sdk
+          mkdir -p "$SDK/bin" # bubblewrap only checks that this exists
+          SM=$ANDROID_HOME/cmdline-tools/latest/bin/sdkmanager
+          yes | "$SM" --sdk_root="$SDK" --licenses >/dev/null || true # yes exits on SIGPIPE
+          "$SM" --sdk_root="$SDK" "build-tools;36.1.0" "platforms;android-36" >/dev/null
+          npm install --global --ignore-scripts @bubblewrap/cli@1.25.0
+          mkdir -p ~/.bubblewrap
+          jq -n --arg jdk "$JAVA_HOME" --arg sdk "$SDK" '{jdkPath:$jdk,androidSdkPath:$sdk}' > ~/.bubblewrap/config.json
+
+      - name: Build + sign
+        env:
+          ANDROID_KEYSTORE_B64: ${{ secrets.ANDROID_KEYSTORE_B64 }}
+          ANDROID_KEY_ALIAS: ${{ secrets.ANDROID_KEY_ALIAS }}
+          BUBBLEWRAP_KEYSTORE_PASSWORD: ${{ secrets.ANDROID_KEYSTORE_PASS }}
+          BUBBLEWRAP_KEY_PASSWORD: ${{ secrets.ANDROID_KEYSTORE_PASS }}
+        run: |
+          B=$RUNNER_TEMP/build OUT=$RUNNER_TEMP/out
+          mkdir -p "$B" "$OUT"
+          echo "$ANDROID_KEYSTORE_B64" | base64 -d > "$B/sune.jks"
+          # pin the icon to this exact commit instead of whatever the site serves today
+          ICON="https://raw.githubusercontent.com/$GITHUB_REPOSITORY/$GITHUB_SHA/public/appstore_content/%E2%9C%BA.png"
+          jq --arg v "$VERSION" --argjson c "$CODE" --arg a "$ANDROID_KEY_ALIAS" --arg i "$ICON" \
+            '.appVersion=$v | .appVersionCode=$c | .signingKey.alias=$a | .iconUrl=$i | .maskableIconUrl=$i' \
+            android/twa-manifest.json > "$B/twa-manifest.json"
+          cd "$B"
+          bubblewrap update --manifest ./twa-manifest.json --skipVersionUpgrade
+          bubblewrap build --manifest ./twa-manifest.json --skipPwaValidation
+          mv app-release-signed.apk "$OUT/$APK"
+          rm -f sune.jks
+          echo "OUT=$OUT" >> $GITHUB_ENV
+
+      - name: Verify the APK
+        run: |
+          cd "$OUT"
+          "$BT/apksigner" verify --verbose --print-certs "$APK" | tee verify.txt
+          grep -q "Number of signers: 1" verify.txt
+          GOT=$(sed -n 's/.*certificate SHA-256 digest: //p' verify.txt | sed -n 1p)
+          WANT=$(jq -r '.[].target | select(.package_name=="chat.sune") | .sha256_cert_fingerprints[]' "$GITHUB_WORKSPACE/public/.well-known/assetlinks.json" | tr -d ':' | tr A-F a-f)
+          [ "$GOT" = "$WANT" ] || { echo "::error::signing cert $GOT does not match assetlinks.json ($WANT)"; exit 1; }
+          "$BT/aapt2" dump badging "$APK" > full-badging.txt
+          grep -m1 '^package:' full-badging.txt | tee badging.txt
+          grep -q "name='chat.sune' versionCode='$CODE' versionName='$VERSION'" badging.txt
+          sha256sum "$APK" | tee "$APK.sha256"
+          echo "SIGNER=$GOT" >> $GITHUB_ENV
+
+      - name: Attest build provenance
+        if: github.ref == 'refs/heads/master'
+        uses: actions/attest-build-provenance@4d101475d8b20a2381f78447822ac1eab6504dd8 # v4.2.2
+        with:
+          subject-path: ${{ runner.temp }}/out/sune-${{ inputs.version }}.apk
+
+      - name: Publish release
+        if: github.ref == 'refs/heads/master'
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          cd "$OUT"
+          SHA=$(cut -d' ' -f1 "$APK.sha256")
+          cat > notes.md <<EOF
+          Built and signed by GitHub Actions from commit \`$GITHUB_SHA\` ([workflow run]($GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID)). Nobody handled the file in between.
+
+          Verify a download:
+          \`\`\`
+          gh attestation verify $APK --repo $GITHUB_REPOSITORY
+          \`\`\`
+
+          - Package: \`chat.sune\`
+          - SHA-256: \`$SHA\`
+          - Signing certificate SHA-256: \`$SIGNER\`
+          EOF
+          gh release create "$TAG" "$APK" "$APK.sha256" --repo "$GITHUB_REPOSITORY" --target "$GITHUB_SHA" --title "Sune $TAG" --notes-file notes.md
+
+      - name: Keep the APK as a workflow artifact (non-release runs)
+        if: github.ref != 'refs/heads/master'
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        with:
+          name: ${{ env.APK }}
+          path: ${{ runner.temp }}/out/*.apk
+          retention-days: 3

android/README.md

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+# Android app
+
+Sune for Android is a [Trusted Web Activity](https://developer.chrome.com/docs/android/trusted-web-activity) wrapper around https://sune.chat, built with [Bubblewrap](https://github.com/GoogleChromeLabs/bubblewrap). It contains no app code, only the config in `twa-manifest.json`.
+
+| | New app | Legacy app (v0.x) |
+|---|---|---|
+| Package | `chat.sune` | `com.planetrenox.sune` |
+| Host | `sune.chat` (also trusts `sune.planetrenox.com`) | `sune.planetrenox.com` |
+| Signing cert SHA-256 | `09:85:1F:7B:BB:40:67:9C:F8:70:1C:7D:9F:65:72:77:78:0E:C0:58:CF:34:09:9A:97:D2:8A:74:FB:CE:87:2A` | `E8:7D:70:60:C2:7D:EF:CB:4D:4D:2B:E2:2E:5E:37:ED:F7:0B:1E:F5:77:D7:04:1F:6B:07:EC:B8:1D:78:6D:43` (**leaked**) |
+
+Both are listed for both domains in [`public/.well-known/assetlinks.json`](../public/.well-known/assetlinks.json); that file is what makes Chrome hide the address bar. Remove the legacy entry once nobody uses the old app (a leaked key can sign a fake `com.planetrenox.sune` that Chrome would trust).
+
+## Releasing
+
+Actions → **Release APK** → Run workflow on `master` → enter the tag, e.g. `v1.0.0`.
+
+It builds `sune-v1.0.0.apk`, signs it, checks the signing cert against `assetlinks.json`, attests build provenance, then creates the tag and release. `versionCode` is `major*10000 + minor*100 + patch`. Run it from any other branch to do a dry run: it builds and verifies but publishes nothing.
+
+## Verifying a download
+
+```bash
+gh attestation verify sune-v1.0.0.apk --repo sune-org/sune
+```
+
+This proves the file was built by this repo's workflow at the commit named in the release, and not modified since. The APK is only a wrapper; the app itself is served live from sune.chat and is not covered by it.
+
+## Signing key
+
+Never in the repo (`*.jks` is gitignored). Repo secrets, read only by `.github/workflows/apk.yml`:
+
+| Secret | What |
+|---|---|
+| `ANDROID_KEYSTORE_B64` | base64 of the PKCS12 keystore (RSA 4096, alias `sune`, valid to 2054) |
+| `ANDROID_KEYSTORE_PASS` | keystore password (also used as the key password) |
+| `ANDROID_KEY_ALIAS` | `sune` |
+
+Losing this key means users can't update `chat.sune` and would have to uninstall and reinstall. Keep an offline copy.

android/twa-manifest.json

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+{
+  "packageId": "chat.sune",
+  "host": "sune.chat",
+  "name": "Sune",
+  "launcherName": "Sune",
+  "display": "standalone",
+  "orientation": "portrait",
+  "themeColor": "#FFFFFF",
+  "themeColorDark": "#FFFFFF",
+  "navigationColor": "#FFFFFF",
+  "navigationColorDark": "#FFFFFF",
+  "navigationDividerColor": "#00000000",
+  "navigationDividerColorDark": "#00000000",
+  "backgroundColor": "#000000",
+  "startUrl": "/",
+  "iconUrl": "https://sune.chat/appstore_content/%E2%9C%BA.png",
+  "maskableIconUrl": "https://sune.chat/appstore_content/%E2%9C%BA.png",
+  "webManifestUrl": "https://sune.chat/manifest.webmanifest",
+  "fullScopeUrl": "https://sune.chat/",
+  "additionalTrustedOrigins": ["https://sune.planetrenox.com"],
+  "enableNotifications": false,
+  "enableSiteSettingsShortcut": false,
+  "splashScreenFadeOutDuration": 300,
+  "fallbackType": "customtabs",
+  "minSdkVersion": 21,
+  "appVersion": "1.0.0",
+  "appVersionCode": 10000,
+  "signingKey": { "path": "./sune.jks", "alias": "sune" },
+  "generatorApp": "bubblewrap-cli"
+}