replay: delay per complete frame instead of per chunk

ReplayPacer (MsgListener+MsgTalker) sits between packetizer output and
downstream listeners; sleeps after each complete NMEA/UBX frame before
forwarding. FileBackend no longer owns the delay — it reads as fast as
possible and the pacer provides back-pressure on the same thread.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

main.py

@@ -8,6 +8,7 @@ from backend.network_backend import NetworkBackend
 from backend.serial_backend  import SerialBackend
 from backend.file_backend    import FileBackend, source_id_from_path
 from msg.frame_logger        import FrameLogger
+from msg.replay_pacer        import ReplayPacer
 from transceiver             import Transceiver
 
 from nmea.packetizer  import NmeaPacketizer
@@ -31,7 +32,7 @@ def parse_args():
 	                help='Save current config as JSON project file')
 	ap.add_argument('--log-dir', default='./log',
 	                help='Frame log directory (default: ./log)')
-	ap.add_argument('--delay', type=float, default=1.0,
+	ap.add_argument('--delay', type=float, default=0.1,
 	                help='File replay inter-frame delay in seconds, 0–10 (default: 1.0)')
 	ap.add_argument('--network', nargs=3, action='append',
 	                metavar=('NAME', 'HOST', 'PORT'),
@@ -86,7 +87,7 @@ def _make_listeners(name: str):
 
 
 def wire_source(name: str, backend, log_dir: str | None,
-                loggers: list, transceivers: dict):
+                loggers: list, transceivers: dict, pacer_delay: float = 0.0):
 	xcvr = Transceiver(name)
 	backend.register_xcvr(xcvr)
 	transceivers[name] = xcvr
@@ -102,10 +103,21 @@ def wire_source(name: str, backend, log_dir: str | None,
 	xcvr.register_listener(ubx_pkt)
 
 	nmea_rx, ubx_rx = _make_listeners(name)
-	for rx in nmea_rx:
-		nmea_pkt.register_listener(rx)
-	for rx in ubx_rx:
-		ubx_pkt.register_listener(rx)
+
+	if pacer_delay > 0:
+		nmea_pacer = ReplayPacer(pacer_delay)
+		ubx_pacer  = ReplayPacer(pacer_delay)
+		nmea_pkt.register_listener(nmea_pacer)
+		ubx_pkt.register_listener(ubx_pacer)
+		for rx in nmea_rx:
+			nmea_pacer.register_listener(rx)
+		for rx in ubx_rx:
+			ubx_pacer.register_listener(rx)
+	else:
+		for rx in nmea_rx:
+			nmea_pkt.register_listener(rx)
+		for rx in ubx_rx:
+			ubx_pkt.register_listener(rx)
 
 
 # ---------------------------------------------------------------------------
@@ -164,13 +176,13 @@ if __name__ == '__main__':
 	# File sources → one shared FileBackend (no secondary logging)
 	file_sources = [s for s in sources if s['type'] == 'file']
 	if file_sources:
-		file_be = FileBackend([s['path'] for s in file_sources], delay=delay)
+		file_be = FileBackend([s['path'] for s in file_sources])
 		backends.append(file_be)
 		for s in file_sources:
 			name = source_id_from_path(s['path'])
 			if name:
 				wire_source(name, file_be, log_dir=None, loggers=loggers,
-				            transceivers=transceivers)
+				            transceivers=transceivers, pacer_delay=delay)
 
 	signal.signal(signal.SIGINT,
 	              lambda sig, frm: handler(sig, frm, backends, loggers))