ci: add engine CI workflow; expose test/fmt tasks; cover engine in check task

- .github/workflows/ci.yml: fmt + lint + typecheck + 35 engine tests on
  push/PR (SHA-pinned actions; setup-deno v2.0.4 resolved from upstream tags)
- deno.json: new test and fmt:check tasks; check task now also covers
  packages/shared/src/matching/

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/ci.yml

@@ -0,0 +1,27 @@
+# SPDX-License-Identifier: MPL-2.0
+name: CI
+on:
+  pull_request:
+  push:
+    branches: [main]
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+permissions:
+  contents: read
+jobs:
+  engine:
+    name: Matching engine + API (fmt, lint, typecheck, tests)
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - uses: denoland/setup-deno@667a34cdef165d8d2b2e98dde39547c9daac7282 # v2.0.4
+        with:
+          deno-version: v2.x
+      - name: Format check (engine)
+        run: deno task fmt:check
+      - name: Lint + typecheck (engine, legacy domain, API)
+        run: deno task check
+      - name: Engine unit tests
+        run: deno task test

deno.json

@@ -12,7 +12,9 @@
     "dev:web": "deno task --cwd apps/web dev",
     "dev:mobile": "echo 'apps/mobile is an Expo project; run `cd apps/mobile && npm install && npm run start` (Expo CLI requires Node — see Class C carve-out in README)'",
     "build:web": "deno task --cwd apps/web build",
-    "check": "deno check apps/api/main.ts && deno lint apps/api && deno check packages/shared/src/domain.js"
+    "check": "deno check apps/api/main.ts && deno lint apps/api && deno check packages/shared/src/domain.js && deno check packages/shared/src/matching/index.js && deno lint packages/shared/src/matching",
+    "test": "deno test --allow-read packages/shared/src/matching/",
+    "fmt:check": "deno fmt --check packages/shared/src/matching/"
   },
   "fmt": {
     "useTabs": false,