feat(observability): add MCP tool name logging in access log

* Include tool name from request in access log entries
* Update user agent header in HTTP requests
* Add tests for MCP tool name logging

internal/observability/http_test.go

@@ -2,6 +2,7 @@ package observability
 
 import (
 	"bytes"
+	"encoding/json"
 	"io"
 	"log/slog"
 	"net/http"
@@ -80,3 +81,36 @@ func TestAccessLogUsesForwardedClientIP(t *testing.T) {
 		t.Fatalf("log output = %q, want remote_addr=203.0.113.7", buf.String())
 	}
 }
+
+func TestAccessLogIncludesMCPToolName(t *testing.T) {
+	var buf bytes.Buffer
+	logger := slog.New(slog.NewTextHandler(&buf, nil))
+	handler := AccessLog(logger)(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusNoContent)
+	}))
+
+	payload := map[string]any{
+		"jsonrpc": "2.0",
+		"id":      "1",
+		"method":  "tools/call",
+		"params": map[string]any{
+			"name":      "list_projects",
+			"arguments": map[string]any{},
+		},
+	}
+	body, err := json.Marshal(payload)
+	if err != nil {
+		t.Fatalf("json.Marshal() error = %v", err)
+	}
+
+	req := httptest.NewRequest(http.MethodPost, "/mcp", bytes.NewReader(body))
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusNoContent {
+		t.Fatalf("status = %d, want %d", rec.Code, http.StatusNoContent)
+	}
+	if !strings.Contains(buf.String(), "tool=list_projects") {
+		t.Fatalf("log output = %q, want tool=list_projects", buf.String())
+	}
+}