chore: add CI workflow with paths-filter and gate job

.github/actions/setup-node-cache/action.yml

@@ -0,0 +1,51 @@
+name: Setup Node.js with cache
+description: Sets up Node.js, caches node_modules and npm, and installs dependencies if needed.
+
+runs:
+  using: composite
+  steps:
+    - uses: actions/setup-node@v6
+      with:
+        node-version-file: .nvmrc
+
+    - name: Compute node modules cache key
+      id: nodeModulesCacheKey
+      shell: bash
+      run: echo "value=$(sha256sum package-lock.json | cut -d ' ' -f 1)" >> $GITHUB_OUTPUT
+
+    - name: Cache node modules
+      id: cacheNodeModules
+      uses: actions/cache@v5
+      with:
+        path: "**/node_modules"
+        key: ${{ runner.os }}-cacheNodeModules20-${{ steps.nodeModulesCacheKey.outputs.value }}
+        restore-keys: ${{ runner.os }}-cacheNodeModules20-
+
+    - name: Get npm cache directory path
+      id: npmCacheDirPath
+      if: ${{ steps.cacheNodeModules.outputs.cache-hit != 'true' }}
+      shell: bash
+      run: echo "dir=$(npm config get cache)" >> $GITHUB_OUTPUT
+
+    - name: Cache npm directory
+      if: ${{ steps.cacheNodeModules.outputs.cache-hit != 'true' }}
+      uses: actions/cache@v5
+      with:
+        path: ${{ steps.npmCacheDirPath.outputs.dir }}
+        key: ${{ runner.os }}-npmCacheDir-${{ steps.nodeModulesCacheKey.outputs.value }}
+        restore-keys: ${{ runner.os }}-npmCacheDir-
+
+    - name: Install system dependencies
+      if: ${{ steps.cacheNodeModules.outputs.cache-hit != 'true' }}
+      shell: bash
+      run: |
+        sudo apt update
+        sudo apt install -y libxkbfile-dev pkg-config libkrb5-dev libxss1
+
+    - name: Install npm dependencies
+      if: ${{ steps.cacheNodeModules.outputs.cache-hit != 'true' }}
+      shell: bash
+      env:
+        PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD: 1
+        ELECTRON_SKIP_BINARY_DOWNLOAD: 1
+      run: npm ci --ignore-scripts

.github/workflows/ci.yml

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+# CI pipeline for pull requests targeting main.
+# Runs four parallel jobs:
+#   - frontend-lint:    ESLint, Stylelint, and hygiene checks
+#   - frontend-compile: TypeScript compilation and layer validation
+#   - backend-lint:     Clippy for the Tauri/Rust backend
+#   - backend-format:   rustfmt check for the Tauri/Rust backend
+#
+# Uses dorny/paths-filter so that each job runs only when relevant files change,
+# while remaining compatible with branch protection required status checks.
+name: CI
+
+on:
+  pull_request:
+    branches: [main]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.ref }}
+  cancel-in-progress: true
+
+permissions: {}
+
+jobs:
+  changes:
+    name: Detect Changes
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    permissions:
+      pull-requests: read
+    outputs:
+      frontend: ${{ steps.filter.outputs.frontend }}
+      backend: ${{ steps.filter.outputs.backend }}
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          persist-credentials: false
+
+      - uses: dorny/paths-filter@v3
+        id: filter
+        with:
+          filters: |
+            frontend:
+              - 'src/**'
+              - 'extensions/**'
+              - 'build/**'
+              - 'test/**'
+              - 'package.json'
+              - 'package-lock.json'
+              - '.nvmrc'
+              - 'eslint.config.js'
+              - '.eslint-ignore'
+              - '.eslint-plugin-local/**'
+              - 'tsfmt.json'
+              - '.editorconfig'
+              - '.github/actions/**'
+              - '.github/workflows/ci.yml'
+            backend:
+              - 'src-tauri/**'
+              - '.github/workflows/ci.yml'
+
+  frontend-lint:
+    name: Frontend Lint
+    needs: changes
+    if: ${{ needs.changes.outputs.frontend == 'true' }}
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    env:
+      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          persist-credentials: false
+
+      - uses: ./.github/actions/setup-node-cache
+
+      - name: ESLint
+        run: npm run eslint
+
+      - name: Stylelint
+        run: npm run stylelint
+
+      - name: Hygiene
+        run: npm run hygiene
+
+  frontend-compile:
+    name: Frontend Compile Check
+    needs: changes
+    if: ${{ needs.changes.outputs.frontend == 'true' }}
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    env:
+      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          persist-credentials: false
+
+      - uses: ./.github/actions/setup-node-cache
+
+      - name: TypeScript compile check
+        run: npm run compile-check-ts-native
+
+      - name: Valid layers check
+        run: npm run valid-layers-check
+
+  backend-lint:
+    name: Backend Lint
+    needs: changes
+    if: ${{ needs.changes.outputs.backend == 'true' }}
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+
+      # Create empty out/ directory so tauri::generate_context!() can resolve frontendDist: "../out"
+      - name: Create frontend dist stub
+        run: mkdir -p out
+
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libgtk-3-dev libwebkit2gtk-4.1-dev libappindicator3-dev librsvg2-dev patchelf
+
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: clippy
+
+      - uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: src-tauri
+
+      - name: Clippy
+        working-directory: src-tauri
+        run: cargo clippy -- -D warnings
+
+  backend-format:
+    name: Backend Format
+    needs: changes
+    if: ${{ needs.changes.outputs.backend == 'true' }}
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          sparse-checkout: |
+            src-tauri
+
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt
+
+      - name: Check format
+        working-directory: src-tauri
+        run: cargo fmt --check
+
+  # Gate job: aggregates all job results into a single required status check.
+  # This job always runs (even when other jobs are skipped by paths-filter),
+  # making it safe to use as a required status check in branch protection.
+  ci-gate:
+    name: CI Gate
+    if: ${{ always() }}
+    needs: [frontend-lint, frontend-compile, backend-lint, backend-format]
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - name: Check job results
+        run: |
+          results=("${{ needs.frontend-lint.result }}" "${{ needs.frontend-compile.result }}" "${{ needs.backend-lint.result }}" "${{ needs.backend-format.result }}")
+          for result in "${results[@]}"; do
+            if [[ "$result" == "failure" || "$result" == "cancelled" ]]; then
+              echo "::error::One or more CI jobs failed or were cancelled."
+              exit 1
+            fi
+          done
+          echo "All CI jobs passed or were skipped."