ci: add GitHub Actions CI for web and pipeline

.github/workflows/ci.yml

@@ -0,0 +1,48 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  web:
+    name: web · typecheck · test · lint · build
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: web
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: npm
+          cache-dependency-path: web/package-lock.json
+      - run: npm ci
+      # No `typecheck` script in web/package.json — call tsc directly.
+      - run: npx tsc --noEmit
+      - run: npm test
+      - run: npm run lint
+      - run: npm run build
+
+  pipeline:
+    name: pipeline · pytest
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v6
+        with:
+          python-version: '3.12'
+          cache: pip
+      - run: pip install -r requirements.txt
+      # soundfile bundles libsndfile in its wheel — no apt install needed.
+      - run: python -m pytest tests/ -q