Fix desktop CI: add icon.ico for Windows, skip macOS codesign, drop macos-13

- Add icons/icon.ico generated from 256x256.png (required for Windows resource file)
- Add icon.ico to bundle.icon list in tauri.conf.json
- Set APPLE_SIGNING_IDENTITY to '-' when APPLE_CERTIFICATE is not configured,
  skipping codesign instead of failing with keychain import error
- Remove macos-13 matrix entry (Intel runners sunset by GitHub)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/desktop.yml

@@ -81,8 +81,6 @@ jobs:
             args: ''
           - platform: macos-latest
             args: '--target aarch64-apple-darwin'
-          - platform: macos-13
-            args: '--target x86_64-apple-darwin'
           - platform: windows-latest
             args: ''
 
@@ -106,7 +104,7 @@ jobs:
       - name: Install Rust stable
         uses: dtolnay/rust-toolchain@stable
         with:
-          targets: ${{ matrix.platform == 'macos-latest' && 'aarch64-apple-darwin' || matrix.platform == 'macos-13' && 'x86_64-apple-darwin' || '' }}
+          targets: ${{ matrix.platform == 'macos-latest' && 'aarch64-apple-darwin' || '' }}
 
       - name: Rust cache
         uses: swatinem/rust-cache@v2
@@ -144,7 +142,7 @@ jobs:
           TAURI_SIGNING_PRIVATE_KEY_PASSWORD: ${{ secrets.TAURI_SIGNING_PRIVATE_KEY_PASSWORD }}
           APPLE_CERTIFICATE: ${{ secrets.APPLE_CERTIFICATE }}
           APPLE_CERTIFICATE_PASSWORD: ${{ secrets.APPLE_CERTIFICATE_PASSWORD }}
-          APPLE_SIGNING_IDENTITY: ${{ secrets.APPLE_SIGNING_IDENTITY }}
+          APPLE_SIGNING_IDENTITY: ${{ secrets.APPLE_CERTIFICATE && secrets.APPLE_SIGNING_IDENTITY || '-' }}
           APPLE_ID: ${{ secrets.APPLE_ID }}
           APPLE_PASSWORD: ${{ secrets.APPLE_PASSWORD }}
           APPLE_TEAM_ID: ${{ secrets.APPLE_TEAM_ID }}

desktop/src-tauri/tauri.conf.json

@@ -38,7 +38,8 @@
     "icon": [
       "icons/32x32.png",
       "icons/128x128.png",
-      "icons/128x128@2x.png"
+      "icons/128x128@2x.png",
+      "icons/icon.ico"
     ],
     "category": "Utility",
     "shortDescription": "On-device AI assistant with energy monitoring and trace debugging",