feat: add Linux Electron release smoke builds

Adds an opt-in input to build Linux Electron artifacts in the smoke workflow
Builds and validates AppImage releases for x64 and arm64
Uploads Linux AppImage and update manifest artifacts

.github/workflows/release-desktop-smoke.yml

@@ -23,6 +23,11 @@ on:
         required: false
         default: true
         type: boolean
+      build_linux:
+        description: Build Linux Electron AppImage artifacts
+        required: false
+        default: true
+        type: boolean
       retention_days:
         description: Artifact retention days
         required: false
@@ -266,3 +271,105 @@ jobs:
             packages/electron/dist/latest.yml
           if-no-files-found: error
           retention-days: ${{ fromJSON(inputs.retention_days) }}
+
+  build-linux-electron:
+    if: ${{ inputs.build_linux }}
+    name: Build Linux Electron (${{ matrix.arch }})
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - runner: ubuntu-24.04
+            arch: x64
+            host_arch: x86_64
+            artifact_arch: x86_64
+            manifest: latest-linux.yml
+          - runner: ubuntu-24.04-arm
+            arch: arm64
+            host_arch: aarch64
+            artifact_arch: arm64
+            manifest: latest-linux-arm64.yml
+    runs-on: ${{ matrix.runner }}
+    steps:
+      - name: Checkout selected ref
+        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+        with:
+          repository: ${{ inputs.repository || github.repository }}
+          ref: ${{ inputs.ref || github.ref }}
+
+      - name: Setup bun
+        uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6 # v2.2.0
+
+      - name: Setup Node.js
+        uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
+        with:
+          node-version: '22'
+
+      - name: Verify native Linux architecture
+        env:
+          EXPECTED_HOST_ARCH: ${{ matrix.host_arch }}
+          OPENCHAMBER_TARGET_ARCH: ${{ matrix.arch }}
+        run: |
+          set -euo pipefail
+          test "$(uname -m)" = "$EXPECTED_HOST_ARCH"
+          test "$(node -p 'process.arch')" = "$OPENCHAMBER_TARGET_ARCH"
+
+      - name: Install dependencies
+        run: bun install --frozen-lockfile
+
+      - name: Get build versions
+        id: versions
+        shell: bash
+        run: |
+          echo "opencode_cli=$(node -p "require('./package.json').dependencies['@opencode-ai/sdk']")" >> "$GITHUB_OUTPUT"
+          echo "app=$(node -p "require('./packages/electron/package.json').version")" >> "$GITHUB_OUTPUT"
+
+      - name: Cache bundled OpenCode CLI artifact
+        uses: actions/cache@0400d5f644dc74513175e3cd8d07132dd4860809 # v4.2.4
+        with:
+          path: packages/electron/.cache/opencode-cli
+          key: opencode-cli-${{ runner.os }}-${{ matrix.arch }}-${{ steps.versions.outputs.opencode_cli }}
+          restore-keys: |
+            opencode-cli-${{ runner.os }}-${{ matrix.arch }}-
+
+      - name: Run focused Electron release tests
+        working-directory: packages/electron
+        run: |
+          bun run test:architecture
+          bun run test:updater
+
+      - name: Build and package Linux AppImage
+        working-directory: packages/electron
+        env:
+          OPENCHAMBER_TARGET_ARCH: ${{ matrix.arch }}
+        run: |
+          set -euo pipefail
+          bun run build:web-assets
+          bun run prepare:opencode-cli
+          bun run verify:opencode-cli
+          bun run bundle:main
+          bun run rebuild:native
+          node ./scripts/package.mjs --linux --${{ matrix.arch }} --publish=never
+          bun run verify:opencode-cli:packaged
+          bun run verify:linux-appimage
+
+      - name: Validate Linux update manifest
+        working-directory: packages/electron
+        env:
+          VERSION: ${{ steps.versions.outputs.app }}
+          ARTIFACT_ARCH: ${{ matrix.artifact_arch }}
+          MANIFEST: ${{ matrix.manifest }}
+        run: |
+          set -euo pipefail
+          APPIMAGE="dist/OpenChamber-${VERSION}-linux-${ARTIFACT_ARCH}.AppImage"
+          node ./scripts/verify-update-manifest.mjs "dist/${MANIFEST}" "$APPIMAGE" "$VERSION"
+
+      - name: Upload Linux installable artifacts
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        with:
+          name: desktop-release-smoke-linux-${{ matrix.arch }}
+          path: |
+            packages/electron/dist/OpenChamber-${{ steps.versions.outputs.app }}-linux-${{ matrix.artifact_arch }}.AppImage
+            packages/electron/dist/${{ matrix.manifest }}
+          if-no-files-found: error
+          retention-days: ${{ fromJSON(inputs.retention_days) }}