ci: add GitHub Actions workflow for testing

Add a CI workflow that runs on every push and pull request to main:
gofmt verification, go vet, race-enabled tests with coverage, library
and example builds, and a benchmark smoke run. The job matrix covers the
module's minimum Go version (1.24.3) and the latest stable release.

Also gofmt-format examples/db-explorer/main.go so the new gofmt gate
passes against the existing tree.

https://claude.ai/code/session_015dqx2yBNNyyfgznEV36bHe

Author: claude

.github/workflows/ci.yml

@@ -0,0 +1,62 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    name: Test (Go ${{ matrix.go-version }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        # Test against the module's minimum supported version and the latest
+        # stable release to catch version-specific regressions.
+        go-version: ['1.24.3', 'stable']
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: ${{ matrix.go-version }}
+
+      - name: Verify gofmt
+        run: |
+          unformatted=$(gofmt -l .)
+          if [ -n "$unformatted" ]; then
+            echo "The following files are not gofmt-formatted:"
+            echo "$unformatted"
+            exit 1
+          fi
+
+      - name: Vet
+        run: go vet ./...
+
+      - name: Test (race + coverage)
+        run: go test ./gomcp/ -race -count=1 -coverprofile=coverage.out -covermode=atomic
+
+      - name: Coverage summary
+        run: go tool cover -func=coverage.out
+
+      - name: Build
+        run: go build ./...
+
+      - name: Build examples
+        # Mirrors the Makefile `examples` target. db-explorer is intentionally
+        # omitted: it is gated behind a build constraint and is not part of the
+        # default build.
+        run: |
+          go build -o /dev/null ./examples/greet/
+          go build -o /dev/null ./examples/sys-monitor/
+          go build -o /dev/null ./examples/fs-navigator/
+
+      - name: Benchmarks (compile + smoke run)
+        run: go test ./gomcp/ -run '^$' -bench . -benchmem -benchtime 10x

examples/db-explorer/main.go

@@ -9,7 +9,9 @@
 //
 // Requires: github.com/lib/pq driver
 // Build:    go build -tags ignore -o db-explorer .
-//           or remove the build tag and: go get github.com/lib/pq
+//
+//	or remove the build tag and: go get github.com/lib/pq
+//
 // Test:     echo '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' | ./db-explorer
 package main
 
@@ -21,8 +23,8 @@ import (
 	"os"
 	"strings"
 
-	_ "github.com/lib/pq"
 	"github.com/BackendStack21/go-mcp/gomcp"
+	_ "github.com/lib/pq"
 )
 
 func main() {