Add Gitea CI workflow for build, test, vet, and lint

Runs on all pushes and PRs:
- Build, vet, and test both root and v2 modules (with -race)
- Verify go.mod/go.sum tidiness for both modules

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitea/workflows/ci.yaml

@@ -0,0 +1,76 @@
+name: CI
+
+on:
+  push:
+    branches: ["*"]
+  pull_request:
+    branches: ["*"]
+
+jobs:
+  root-module:
+    name: Root Module
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version: "1.24"
+
+      - name: Download dependencies
+        run: go mod download
+
+      - name: Build
+        run: go build ./...
+
+      - name: Vet
+        run: go vet ./...
+
+      - name: Test
+        run: go test -race -count=1 ./...
+
+  v2-module:
+    name: V2 Module
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: v2
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version: "1.24"
+
+      - name: Download dependencies
+        run: go mod download
+
+      - name: Build
+        run: go build ./...
+
+      - name: Vet
+        run: go vet ./...
+
+      - name: Test
+        run: go test -race -count=1 ./...
+
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version: "1.24"
+
+      - name: Check root module tidiness
+        run: |
+          go mod tidy
+          git diff --exit-code go.mod go.sum
+
+      - name: Check v2 module tidiness
+        run: |
+          cd v2
+          go mod tidy
+          git diff --exit-code go.mod go.sum