fix(lint): check resp.Body.Close error in bearer_test.go

Silences errcheck violations that have been breaking CI since the test
was written.

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

internal/auth/bearer_test.go

@@ -20,7 +20,7 @@ func TestBearerMiddleware_NoAuthHeader(t *testing.T) {
 
 	resp, err := http.Post(srv.URL+"/mcp", "application/json", nil)
 	require.NoError(t, err)
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 	assert.Equal(t, http.StatusUnauthorized, resp.StatusCode)
 }
 
@@ -42,7 +42,7 @@ func TestBearerMiddleware_InvalidToken(t *testing.T) {
 	req.Header.Set("Authorization", "Bearer bad-token")
 	resp, err := http.DefaultClient.Do(req)
 	require.NoError(t, err)
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 	assert.Equal(t, http.StatusUnauthorized, resp.StatusCode)
 }
 
@@ -71,7 +71,7 @@ func TestBearerMiddleware_ValidToken(t *testing.T) {
 	req.Header.Set("Authorization", "Bearer "+token)
 	resp, err := http.DefaultClient.Do(req)
 	require.NoError(t, err)
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 	assert.Equal(t, http.StatusOK, resp.StatusCode)
 	assert.True(t, called)
 }