fix: address code review — error-path tests, edge cases, UX improvements

internal/infra/git/branch.go

@@ -52,7 +52,7 @@ func parseRemoteBranches(buf []byte) []string {
 	var branches []string
 	sc := bufio.NewScanner(bytes.NewReader(buf))
 	for sc.Scan() {
-		line := sc.Text()
+		line := strings.TrimSpace(sc.Text())
 		if idx := strings.Index(line, "\trefs/heads/"); idx >= 0 {
 			name := line[idx+len("\trefs/heads/"):]
 			if name != "" {

internal/infra/git/branch_test.go

@@ -8,7 +8,7 @@ import (
 
 func TestParseRemoteBranches(t *testing.T) {
 	t.Parallel()
-	input := []byte("aabbccdd\trefs/heads/main\n" +
+	input := []byte("aabbccdd\trefs/heads/main\r\n" +
 		"eeff0011\trefs/heads/develop\n" +
 		"22334455\trefs/heads/feature/foo\n" +
 		"deadbeef\trefs/tags/v1.0\n")