feat: Update gh-pages README with latest mobile release links (#1003)

Add steps to the mobile-release workflow that checkout the gh-pages
branch and update its README.md with direct download links to the
latest Flutter mobile clients (Android APK, debug APK, iOS unsigned
build). Uses HTML comment markers for idempotent updates on subsequent
releases.

https://claude.ai/code/session_01GuUjjmMzxvdSwfvhrjvJr1

Co-authored-by: Claude <noreply@anthropic.com>

.github/workflows/mobile-release.yml

@@ -111,4 +111,85 @@ jobs:
             - **Android APK**: Debug build for testing on Android devices
             - **iOS Build**: Unsigned iOS build (requires code signing for installation)
 
-            > **Note**: These are builds intended for testing purposes. For production use, please build from source with proper signing credentials.
+            > **Note**: These are builds intended for testing purposes. For production use, please build from source with proper signing credentials.
+
+      - name: Checkout gh-pages branch
+        uses: actions/checkout@v4
+        with:
+          ref: gh-pages
+          path: gh-pages
+
+      - name: Update README with latest mobile release links
+        run: |
+          set -euo pipefail
+          VERSION="${{ steps.version.outputs.version }}"
+          TAG="${{ github.ref_name }}"
+          REPO="${{ github.repository }}"
+
+          # Build download links based on which assets were produced
+          LINKS=""
+          if [ -f "${{ runner.temp }}/release-assets/sure-${VERSION}.apk" ]; then
+            LINKS="${LINKS}- **Android APK**: [sure-${VERSION}.apk](https://github.com/${REPO}/releases/download/${TAG}/sure-${VERSION}.apk)\n"
+          fi
+          if [ -f "${{ runner.temp }}/release-assets/sure-${VERSION}-debug.apk" ]; then
+            LINKS="${LINKS}- **Android Debug APK**: [sure-${VERSION}-debug.apk](https://github.com/${REPO}/releases/download/${TAG}/sure-${VERSION}-debug.apk)\n"
+          fi
+          if [ -f "${{ runner.temp }}/release-assets/sure-${VERSION}-ios-unsigned.zip" ]; then
+            LINKS="${LINKS}- **iOS Build (unsigned)**: [sure-${VERSION}-ios-unsigned.zip](https://github.com/${REPO}/releases/download/${TAG}/sure-${VERSION}-ios-unsigned.zip)\n"
+          fi
+
+          # Build the mobile downloads section
+          SECTION="$(cat <<BLOCK
+          <!-- MOBILE_DOWNLOADS_START -->
+          ## Latest Mobile Release: ${VERSION}
+
+          **Release page**: [${TAG}](https://github.com/${REPO}/releases/tag/${TAG})
+
+          ### Direct Downloads
+
+          $(echo -e "$LINKS")
+
+          > **Note**: These are builds intended for testing purposes. For production use, please build from source with proper signing credentials.
+          <!-- MOBILE_DOWNLOADS_END -->
+          BLOCK
+          )"
+
+          # Strip leading whitespace from heredoc indentation
+          SECTION="$(echo "$SECTION" | sed 's/^          //')"
+
+          README="gh-pages/README.md"
+
+          if [ ! -f "$README" ]; then
+            # No README yet — create one
+            printf "# Sure\n\n%s\n" "$SECTION" > "$README"
+          elif grep -q '<!-- MOBILE_DOWNLOADS_START -->' "$README"; then
+            # Replace existing mobile section between markers
+            awk '
+              /<!-- MOBILE_DOWNLOADS_START -->/ { skip=1; next }
+              /<!-- MOBILE_DOWNLOADS_END -->/   { skip=0; next }
+              !skip { print }
+            ' "$README" > "${README}.tmp"
+
+            # Re-insert the updated section at the end
+            printf "%s\n\n%s\n" "$(cat "${README}.tmp")" "$SECTION" > "$README"
+            rm "${README}.tmp"
+          else
+            # Append mobile section to existing README
+            printf "\n%s\n" "$SECTION" >> "$README"
+          fi
+
+          echo "Updated README.md:"
+          cat "$README"
+
+      - name: Push updated README to gh-pages
+        run: |
+          cd gh-pages
+          git config user.name "${{ github.actor }}"
+          git config user.email "${{ github.actor }}@users.noreply.github.com"
+          git add README.md
+          if git diff --cached --quiet; then
+            echo "No README changes to push."
+            exit 0
+          fi
+          git commit -m "Update mobile download links for ${{ steps.version.outputs.version }}"
+          git push