fix: add test parallelism and increase Windows CI timeout

- Increase Windows test timeout from 20m to 30m
- Add -parallel=4 flag to allow concurrent test execution
- Add t.Parallel() to safe table-driven tests in validate_test.go,
  autoimport_test.go, and sync_test.go

This should prevent the Windows CI timeout caused by the cumulative
runtime of cmd/bd tests exceeding 20 minutes.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

cmd/bd/autoimport_test.go

@@ -283,6 +283,7 @@ func TestCheckGitForIssues_NoBeadsDir(t *testing.T) {
 }
 
 func TestBoolToFlag(t *testing.T) {
+	t.Parallel()
 	tests := []struct {
 		name      string
 		condition bool
@@ -296,7 +297,9 @@ func TestBoolToFlag(t *testing.T) {
 	}
 
 	for _, tt := range tests {
+		tt := tt // capture range variable
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
 			got := boolToFlag(tt.condition, tt.flag)
 			if got != tt.want {
 				t.Errorf("boolToFlag(%v, %q) = %q, want %q", tt.condition, tt.flag, got, tt.want)