ci: add GitHub Actions workflow for common platform

Three parallel job groups (NO deployment):
- build-and-test: full build + typecheck + test + lint
- package-tests: matrix of 9 @bytelyst/* packages
- service-tests: matrix of 4 @lysnrai/* services

Uses pnpm v10, Node 20, dependency caching.
Runs on push/PR to main with concurrency cancellation.

.github/workflows/ci.yml

@@ -0,0 +1,161 @@
+name: CI — Common Platform
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+# Cancel in-progress runs for the same branch/PR
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build-and-test:
+    name: Build, Test & Typecheck
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Setup pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 10
+
+      - name: Get pnpm store directory
+        shell: bash
+        run: echo "STORE_PATH=$(pnpm store path --silent)" >> $GITHUB_ENV
+
+      - name: Cache pnpm dependencies
+        uses: actions/cache@v4
+        with:
+          path: ${{ env.STORE_PATH }}
+          key: ${{ runner.os }}-pnpm-store-${{ hashFiles('**/pnpm-lock.yaml') }}
+          restore-keys: |
+            ${{ runner.os }}-pnpm-store-
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Build all packages and services
+        run: pnpm build
+
+      - name: Typecheck
+        run: pnpm typecheck
+
+      - name: Run tests
+        run: pnpm test
+
+      - name: Lint
+        run: pnpm lint
+
+  # Per-package test breakdown (runs in parallel with main job)
+  package-tests:
+    name: Package Tests
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    strategy:
+      fail-fast: false
+      matrix:
+        package:
+          - errors
+          - cosmos
+          - config
+          - auth
+          - api-client
+          - react-auth
+          - fastify-core
+          - design-tokens
+          - testing
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Setup pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 10
+
+      - name: Get pnpm store directory
+        shell: bash
+        run: echo "STORE_PATH=$(pnpm store path --silent)" >> $GITHUB_ENV
+
+      - name: Cache pnpm dependencies
+        uses: actions/cache@v4
+        with:
+          path: ${{ env.STORE_PATH }}
+          key: ${{ runner.os }}-pnpm-store-${{ hashFiles('**/pnpm-lock.yaml') }}
+          restore-keys: |
+            ${{ runner.os }}-pnpm-store-
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Build (packages depend on each other)
+        run: pnpm build
+
+      - name: Test @bytelyst/${{ matrix.package }}
+        run: pnpm --filter @bytelyst/${{ matrix.package }} test
+
+  service-tests:
+    name: Service Tests
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    strategy:
+      fail-fast: false
+      matrix:
+        service:
+          - platform-service
+          - billing-service
+          - growth-service
+          - tracker-service
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Setup pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 10
+
+      - name: Get pnpm store directory
+        shell: bash
+        run: echo "STORE_PATH=$(pnpm store path --silent)" >> $GITHUB_ENV
+
+      - name: Cache pnpm dependencies
+        uses: actions/cache@v4
+        with:
+          path: ${{ env.STORE_PATH }}
+          key: ${{ runner.os }}-pnpm-store-${{ hashFiles('**/pnpm-lock.yaml') }}
+          restore-keys: |
+            ${{ runner.os }}-pnpm-store-
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Build
+        run: pnpm build
+
+      - name: Test @lysnrai/${{ matrix.service }}
+        run: pnpm --filter @lysnrai/${{ matrix.service }} test