fix(lint): satisfy errcheck for io.Copy, json.Encode, Body.Close, deferred Close

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

internal/mcp/server.go

@@ -80,7 +80,7 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	w.Header().Set("Content-Type", "application/json")
-	json.NewEncoder(w).Encode(response{
+	_ = json.NewEncoder(w).Encode(response{
 		JSONRPC: "2.0",
 		ID:      req.ID,
 		Result:  result,
@@ -90,7 +90,7 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 func writeError(w http.ResponseWriter, id any, code int, msg string) {
 	w.Header().Set("Content-Type", "application/json")
-	json.NewEncoder(w).Encode(response{
+	_ = json.NewEncoder(w).Encode(response{
 		JSONRPC: "2.0",
 		ID:      id,
 		Error:   &rpcError{Code: code, Message: msg},

internal/session/session.go

@@ -73,7 +73,7 @@ func Read(sessionsDir, sessionID string) ([]Entry, error) {
 	if err != nil {
 		return nil, fmt.Errorf("open session log: %w", err)
 	}
-	defer f.Close()
+	defer f.Close() //nolint:errcheck
 
 	var entries []Entry
 	scanner := bufio.NewScanner(f)

internal/skills/brain/handlers_test.go

@@ -18,7 +18,7 @@ func TestHandle_BrainQuery_CallsIngestServer(t *testing.T) {
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		assert.Equal(t, "/query", r.URL.Path)
 		called = true
-		json.NewEncoder(w).Encode(map[string]any{
+		_ = json.NewEncoder(w).Encode(map[string]any{
 			"results": []map[string]any{
 				{"path": "wiki/concepts/tdd.md", "title": "TDD", "excerpt": "Test-driven development.", "score": 3},
 			},