Add protocol module, video-node binary, query/web CLI tools

- Protocol module: framed binary encoding for control requests/responses
  (ENUM_DEVICES, ENUM_CONTROLS, GET/SET_CONTROL, STREAM_OPEN/CLOSE)
- video-node: scans /dev/media* and /dev/video*, serves V4L2 device
  topology and controls over TCP; uses UDP discovery for peer announce
- query_cli: auto-discovers a node, queries devices and controls
- protocol_cli: low-level protocol frame decoder for debugging
- dev/web: Express 5 ESM web inspector — live SSE discovery picker,
  REST bridge to video-node, controls UI with sliders/selects/checkboxes
- Makefile: sequential module builds before cli/node to fix make -j races
- common.mk: add DEPFLAGS (-MMD -MP) for automatic header dependencies
- All module Makefiles: split compile/link, generate .d dependency files
- discovery: replace 100ms poll loop with pthread_cond_timedwait;
  respond to all announcements (not just new peers) for instant re-discovery
- ENUM_DEVICES response: carry device_caps (V4L2_CAP_*) per video node
  so clients can distinguish capture nodes from metadata nodes

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

dev/cli/Makefile

@@ -9,47 +9,79 @@ SERIAL_OBJ       = $(BUILD)/serial/serial.o
 TRANSPORT_OBJ    = $(BUILD)/transport/transport.o
 DISCOVERY_OBJ    = $(BUILD)/discovery/discovery.o
 CONFIG_OBJ       = $(BUILD)/config/config.o
+PROTOCOL_OBJ     = $(BUILD)/protocol/protocol.o
 
-.PHONY: all clean modules
+CLI_SRCS = \
+	media_ctrl_cli.c \
+	v4l2_ctrl_cli.c \
+	transport_cli.c \
+	discovery_cli.c \
+	config_cli.c \
+	protocol_cli.c \
+	query_cli.c
 
-all: modules \
+CLI_OBJS = $(CLI_SRCS:%.c=$(CLI_BUILD)/%.o)
+
+.PHONY: all clean
+
+all: \
 	$(CLI_BUILD)/media_ctrl_cli \
 	$(CLI_BUILD)/v4l2_ctrl_cli \
 	$(CLI_BUILD)/transport_cli \
 	$(CLI_BUILD)/discovery_cli \
-	$(CLI_BUILD)/config_cli
+	$(CLI_BUILD)/config_cli \
+	$(CLI_BUILD)/protocol_cli \
+	$(CLI_BUILD)/query_cli
 
-modules:
-	$(MAKE) -C $(ROOT)/src/modules/common
-	$(MAKE) -C $(ROOT)/src/modules/media_ctrl
-	$(MAKE) -C $(ROOT)/src/modules/v4l2_ctrl
-	$(MAKE) -C $(ROOT)/src/modules/serial
-	$(MAKE) -C $(ROOT)/src/modules/transport
-	$(MAKE) -C $(ROOT)/src/modules/discovery
-	$(MAKE) -C $(ROOT)/src/modules/config
+# Module objects delegate to their sub-makes.
+$(COMMON_OBJ):    ; $(MAKE) -C $(ROOT)/src/modules/common
+$(MEDIA_CTRL_OBJ):; $(MAKE) -C $(ROOT)/src/modules/media_ctrl
+$(V4L2_CTRL_OBJ): ; $(MAKE) -C $(ROOT)/src/modules/v4l2_ctrl
+$(SERIAL_OBJ):    ; $(MAKE) -C $(ROOT)/src/modules/serial
+$(TRANSPORT_OBJ): ; $(MAKE) -C $(ROOT)/src/modules/transport
+$(DISCOVERY_OBJ): ; $(MAKE) -C $(ROOT)/src/modules/discovery
+$(CONFIG_OBJ):    ; $(MAKE) -C $(ROOT)/src/modules/config
+$(PROTOCOL_OBJ):  ; $(MAKE) -C $(ROOT)/src/modules/protocol
 
-$(CLI_BUILD)/media_ctrl_cli: media_ctrl_cli.c $(COMMON_OBJ) $(MEDIA_CTRL_OBJ) | $(CLI_BUILD)
+# Compile each CLI source to its own .o (generates .d alongside).
+$(CLI_BUILD)/%.o: %.c | $(CLI_BUILD)
+	$(CC) $(CFLAGS) $(DEPFLAGS) -c -o $@ $<
+
+# Link rules.
+$(CLI_BUILD)/media_ctrl_cli: $(CLI_BUILD)/media_ctrl_cli.o $(COMMON_OBJ) $(MEDIA_CTRL_OBJ)
 	$(CC) $(CFLAGS) -o $@ $^
 
-$(CLI_BUILD)/v4l2_ctrl_cli: v4l2_ctrl_cli.c $(COMMON_OBJ) $(V4L2_CTRL_OBJ) | $(CLI_BUILD)
+$(CLI_BUILD)/v4l2_ctrl_cli: $(CLI_BUILD)/v4l2_ctrl_cli.o $(COMMON_OBJ) $(V4L2_CTRL_OBJ)
 	$(CC) $(CFLAGS) -o $@ $^
 
-$(CLI_BUILD)/transport_cli: transport_cli.c $(COMMON_OBJ) $(SERIAL_OBJ) $(TRANSPORT_OBJ) | $(CLI_BUILD)
+$(CLI_BUILD)/transport_cli: $(CLI_BUILD)/transport_cli.o $(COMMON_OBJ) $(SERIAL_OBJ) $(TRANSPORT_OBJ)
 	$(CC) $(CFLAGS) -o $@ $^ -lpthread
 
-$(CLI_BUILD)/discovery_cli: discovery_cli.c $(COMMON_OBJ) $(SERIAL_OBJ) $(DISCOVERY_OBJ) | $(CLI_BUILD)
+$(CLI_BUILD)/discovery_cli: $(CLI_BUILD)/discovery_cli.o $(COMMON_OBJ) $(SERIAL_OBJ) $(DISCOVERY_OBJ)
 	$(CC) $(CFLAGS) -o $@ $^ -lpthread
 
-$(CLI_BUILD)/config_cli: config_cli.c $(COMMON_OBJ) $(CONFIG_OBJ) | $(CLI_BUILD)
+$(CLI_BUILD)/config_cli: $(CLI_BUILD)/config_cli.o $(COMMON_OBJ) $(CONFIG_OBJ)
 	$(CC) $(CFLAGS) -o $@ $^
 
+$(CLI_BUILD)/protocol_cli: $(CLI_BUILD)/protocol_cli.o $(COMMON_OBJ) $(SERIAL_OBJ) $(TRANSPORT_OBJ) $(PROTOCOL_OBJ)
+	$(CC) $(CFLAGS) -o $@ $^ -lpthread
+
+$(CLI_BUILD)/query_cli: $(CLI_BUILD)/query_cli.o $(COMMON_OBJ) $(SERIAL_OBJ) $(TRANSPORT_OBJ) $(DISCOVERY_OBJ) $(PROTOCOL_OBJ)
+	$(CC) $(CFLAGS) -o $@ $^ -lpthread
+
 $(CLI_BUILD):
 	mkdir -p $@
 
 clean:
 	rm -f \
+		$(CLI_OBJS) \
+		$(CLI_OBJS:%.o=%.d) \
 		$(CLI_BUILD)/media_ctrl_cli \
 		$(CLI_BUILD)/v4l2_ctrl_cli \
 		$(CLI_BUILD)/transport_cli \
 		$(CLI_BUILD)/discovery_cli \
-		$(CLI_BUILD)/config_cli
+		$(CLI_BUILD)/config_cli \
+		$(CLI_BUILD)/protocol_cli \
+		$(CLI_BUILD)/query_cli
+
+-include $(CLI_OBJS:%.o=%.d)