fix: address review feedback — restore timer.Stop() and fix test spacing

- Restore timer.Stop() no-op in case <-timer.C for symmetry with ctx.Done
- Add missing blank line between TestNoInsecureOption_RejectsHTTP and
  TestNoInsecureOption_RejectsUppercaseHTTP
- Remove double blank line before TestAllowInsecureHTTP_WithoutEnvVar_Rejected

Resolves review comments from sonnet-review-bot on PR #113.

github/client.go

@@ -319,6 +319,7 @@ func (c *Client) doRequest(ctx context.Context, method, reqURL string, accept st
 				timer := time.NewTimer(delay)
 				select {
 				case <-timer.C:
+					timer.Stop() // no-op after fire; kept for symmetry with the ctx.Done case
 				case <-ctx.Done():
 					timer.Stop()
 					return nil, ctx.Err()

github/client_test.go

@@ -544,6 +544,7 @@ func TestNoInsecureOption_RejectsHTTP(t *testing.T) {
 		t.Errorf("unexpected error message: %v", err)
 	}
 }
+
 func TestNoInsecureOption_RejectsUppercaseHTTP(t *testing.T) {
 	// Verify case-insensitive scheme check (RFC 3986).
 	c := NewClient("tok", "HTTP://example.com")
@@ -568,7 +569,6 @@ func TestNoInsecureOption_RejectsMixedCaseHTTP(t *testing.T) {
 	}
 }
 
-
 func TestAllowInsecureHTTP_WithoutEnvVar_Rejected(t *testing.T) {
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		t.Fatal("request should not have been sent")