ci: cache electron + electron-builder tool downloads on release (#1110)

electron-builder fetches the Electron binary and its platform tools
(notarytool, winCodeSign, nsis, squirrel, AppImage) on every run.
Cache those per-platform so repeat releases skip the re-download.
Saves ~30-90s per job, including the macOS long pole.

Key includes pnpm-lock.yaml so a bump to electron/electron-builder
invalidates stale cached binaries; restore-keys falls back to the
latest per-platform cache in between lockfile changes.

Co-authored-by: Orca <help@stably.ai>

.github/workflows/release.yml

@@ -86,12 +86,21 @@ jobs:
           - os: macos-15
             platform: mac
             release_command: ORCA_MAC_RELEASE=1 pnpm exec electron-builder --config config/electron-builder.config.cjs --mac --publish always
+            eb_cache_path: |
+              ~/Library/Caches/electron
+              ~/Library/Caches/electron-builder
           - os: windows-latest
             platform: win
             release_command: pnpm exec electron-builder --config config/electron-builder.config.cjs --win --publish always
+            eb_cache_path: |
+              ~\AppData\Local\electron\Cache
+              ~\AppData\Local\electron-builder\Cache
           - os: ubuntu-latest
             platform: linux
             release_command: pnpm exec electron-builder --config config/electron-builder.config.cjs --linux --publish always
+            eb_cache_path: |
+              ~/.cache/electron
+              ~/.cache/electron-builder
 
     runs-on: ${{ matrix.os }}
 
@@ -116,6 +125,16 @@ jobs:
           node-version-file: .nvmrc
           cache: pnpm
 
+      # Cache the Electron binary + electron-builder tool downloads (notarytool,
+      # winCodeSign, nsis, squirrel, AppImage). Saves ~30-90s per job, incl. mac.
+      - name: Cache electron-builder downloads
+        uses: actions/cache@v4
+        with:
+          path: ${{ matrix.eb_cache_path }}
+          key: electron-builder-${{ matrix.platform }}-${{ hashFiles('pnpm-lock.yaml') }}
+          restore-keys: |
+            electron-builder-${{ matrix.platform }}-
+
       # Why: pnpm install triggers electron's postinstall, which downloads the
       # Electron binary from GitHub release assets. GitHub's download CDN
       # occasionally returns 504s that fail the whole release. Retry on