fix(gemini-test): use ProgressCallback to make resume tests deterministic

internal/protocol/gemini/gemini_test.go

@@ -218,18 +218,29 @@ func TestGeminiResumeSaveMetadata(t *testing.T) {
 	u, _ := url.Parse("gemini://127.0.0.1:" + strconv.Itoa(port) + "/")
 
 	ctx, cancel := context.WithCancel(context.Background())
+	// progress is signalled every time the download loop calls
+	// req.ProgressCallback — which happens *after* a successful
+	// writer.Write. Reading from it is therefore a deterministic
+	// barrier waiting for the first byte to land on disk.
+	progress := make(chan int64, 1)
 	errCh := make(chan error, 1)
 	go func() {
 		_, err := proto.Download(ctx, &core.DownloadRequest{
 			URL:    u,
 			Output: outPath,
+			ProgressCallback: func(current, total int64, speed float64) {
+				select {
+				case progress <- current:
+				default:
+				}
+			},
 		})
 		errCh <- err
 	}()
 
-	// Cancel mid-download — the slow server keeps the connection open
-	// long enough for the cancellation to fire between reads.
-	time.Sleep(150 * time.Millisecond)
+	// Wait until the first byte has been written to disk, then cancel.
+	// No fixed sleep — this is robust against slow CI schedulers.
+	<-progress
 	cancel()
 
 	err = <-errCh
@@ -307,17 +318,26 @@ func TestGeminiResumeDownload(t *testing.T) {
 	u, _ := url.Parse("gemini://127.0.0.1:" + strconv.Itoa(port) + "/data")
 
 	// First attempt: the server sends 500 bytes and blocks. We cancel
-	// the context, then the server closes the connection.
+	// the context, then the server closes the connection. progress
+	// signals after the first writer.Write so waiting on it replaces
+	// the previous fixed sleep with a deterministic barrier.
 	ctx1, cancel1 := context.WithCancel(context.Background())
+	progress := make(chan int64, 1)
 	errCh := make(chan error, 1)
 	go func() {
 		_, dlErr := proto.Download(ctx1, &core.DownloadRequest{
 			URL:    u,
 			Output: outPath,
+			ProgressCallback: func(current, total int64, speed float64) {
+				select {
+				case progress <- current:
+				default:
+				}
+			},
 		})
 		errCh <- dlErr
 	}()
-	time.Sleep(100 * time.Millisecond)
+	<-progress
 	cancel1()
 	cancelReady <- struct{}{} // let server close connection
 	<-connReady