chore(ci): add shared-lib scaffolding and functional coverage gate (#4)

.gitea/workflows/ci.yaml

@@ -20,7 +20,79 @@ jobs:
           go install mvdan.cc/gofumpt@latest
           test -z "$(gofumpt -l .)"
       - name: Run tests
-        run: go test -race ./...
+        run: go test -race -coverprofile=coverage.txt ./...
+
+      - name: Filter test files from coverage
+        run: |
+          grep -v -E '_test\.go:' coverage.txt > coverage.filtered.txt || true
+          mv coverage.filtered.txt coverage.txt
+
+      - name: Check coverage
+        id: coverage
+        run: |
+          go install github.com/vladopajic/go-test-coverage/v2@latest
+          go-test-coverage --config ./.testcoverage.yml --github-action-output
+      - name: Restore baseline coverage
+        uses: actions/cache/restore@v5
+        with:
+          path: coverage-baseline.txt
+          key: coverage-baseline-${{ gitea.run_id }}
+          restore-keys: |
+            coverage-baseline-
+      - name: Compare coverage
+        run: |
+          CURRENT="${{ steps.coverage.outputs.total-coverage }}"
+          if [ -f coverage-baseline.txt ]; then
+            BASE=$(cat coverage-baseline.txt)
+            echo "Base coverage: ${BASE}%"
+            echo "Current coverage: ${CURRENT}%"
+            if [ "$(echo "$CURRENT < $BASE" | bc -l)" -eq 1 ]; then
+              echo "::error::Coverage decreased from ${BASE}% to ${CURRENT}%"
+              exit 1
+            fi
+            echo "Coverage maintained or improved: ${BASE}% -> ${CURRENT}%"
+          else
+            echo "No baseline coverage found yet, skipping comparison"
+            echo "Current coverage: ${CURRENT}%"
+          fi
+      - name: Post coverage comment
+        env:
+          GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
+          GITEA_URL: ${{ gitea.server_url }}
+        run: |
+          COVERAGE="${{ steps.coverage.outputs.total-coverage }}"
+          curl -X POST "${GITEA_URL}/api/v1/repos/${{ gitea.repository }}/issues/${{ gitea.event.pull_request.number }}/comments" \
+            -H "Authorization: token ${GITEA_TOKEN}" \
+            -H "Content-Type: application/json" \
+            -d "{\"body\": \"## Coverage Report\n\nTotal coverage: **${COVERAGE}%**\"}"
+
+  coverage-baseline:
+    # Records main's coverage into the Actions cache for the next PR's
+    # regression gate to read. Post-merge only, not a required check, blocks
+    # nothing (cf. ADR-0010).
+    if: gitea.event_name == 'push'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-go@v6
+        with:
+          go-version: 'stable'
+      - name: Compute coverage
+        id: coverage
+        run: |
+          go install github.com/vladopajic/go-test-coverage/v2@latest
+          go test -coverprofile=coverage.txt ./...
+          grep -v -E '_test\.go:' coverage.txt > coverage.filtered.txt || true
+          mv coverage.filtered.txt coverage.txt
+          go-test-coverage --config ./.testcoverage.yml --github-action-output
+      - name: Write baseline file
+        run: echo "${{ steps.coverage.outputs.total-coverage }}" > coverage-baseline.txt
+      - name: Save baseline to cache
+        uses: actions/cache/save@v5
+        with:
+          path: coverage-baseline.txt
+          key: coverage-baseline-${{ gitea.run_id }}
+
   vulnerabilities:
     if: gitea.event_name == 'pull_request'
     runs-on: ubuntu-latest