ci: 起 GitHub Actions — build + vet + make guard + test-race

最小可跑 CI。ubuntu-latest + setup-go@v5 + Go 1.23，模块缓存开启。push/PR
到 main 触发；同 ref 并发取消；10 min 超时。不依赖 Docker / Postgres
（集成测试留 testcontainers PR）。

闭掉 harness-health W3 partial 的前置条件之一。

.github/workflows/ci.yml

@@ -0,0 +1,44 @@
+name: ci
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build-test:
+    name: build + vet + guard + race
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.23'
+          cache: true
+
+      - name: Download modules
+        run: go mod download
+
+      - name: Build
+        run: go build ./...
+
+      - name: Vet
+        run: go vet ./...
+
+      - name: Guard (G1/G6/G11/G12/G13)
+        run: make guard
+
+      - name: Test (race)
+        run: go test -race -timeout 5m ./...