fix(rename-prefix): sync JSONL before and after prefix rename (#893)

- Pull from sync-branch before rename if configured
- Import all issues from JSONL before rename to prevent data loss
- Export directly to JSONL after rename (don't rely on flushManager)
- Apply same pattern to --repair mode
- Add newSilentLogger() for production use (not test-only)
- Add comprehensive tests for JSONL update scenarios

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

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

cmd/bd/daemon_logger.go

@@ -149,6 +149,12 @@ func SetupStderrLogger(jsonFormat bool, level slog.Level) daemonLogger {
 // newTestLogger creates a no-op logger for testing.
 // Logs are discarded - use this when you don't need to verify log output.
 func newTestLogger() daemonLogger {
+	return newSilentLogger()
+}
+
+// newSilentLogger creates a logger that discards all output.
+// Use this for operations that need a logger but shouldn't produce output.
+func newSilentLogger() daemonLogger {
 	return daemonLogger{
 		logger: slog.New(slog.NewTextHandler(io.Discard, nil)),
 	}