Add config module: INI loader with schema-driven defaults

Config_Def schema tables declare section/key/type/default per module.
Typed getters: config_get_str, _u16, _u32, _flags.
FLAGS type parses space/comma-separated tokens via a Config_Flag_Def table.
config_defaults() gives schema defaults without a file.
config_dump() prints effective values for diagnostics.

config_cli: load a file or --defaults and dump effective config.
dev/example.cfg: sample config covering node, discovery, transport.

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

dev/cli/Makefile

@@ -8,6 +8,7 @@ V4L2_CTRL_OBJ    = $(BUILD)/v4l2_ctrl/v4l2_ctrl.o
 SERIAL_OBJ       = $(BUILD)/serial/serial.o
 TRANSPORT_OBJ    = $(BUILD)/transport/transport.o
 DISCOVERY_OBJ    = $(BUILD)/discovery/discovery.o
+CONFIG_OBJ       = $(BUILD)/config/config.o
 
 .PHONY: all clean modules
 
@@ -15,7 +16,8 @@ all: modules \
 	$(CLI_BUILD)/media_ctrl_cli \
 	$(CLI_BUILD)/v4l2_ctrl_cli \
 	$(CLI_BUILD)/transport_cli \
-	$(CLI_BUILD)/discovery_cli
+	$(CLI_BUILD)/discovery_cli \
+	$(CLI_BUILD)/config_cli
 
 modules:
 	$(MAKE) -C $(ROOT)/src/modules/common
@@ -24,6 +26,7 @@ modules:
 	$(MAKE) -C $(ROOT)/src/modules/serial
 	$(MAKE) -C $(ROOT)/src/modules/transport
 	$(MAKE) -C $(ROOT)/src/modules/discovery
+	$(MAKE) -C $(ROOT)/src/modules/config
 
 $(CLI_BUILD)/media_ctrl_cli: media_ctrl_cli.c $(COMMON_OBJ) $(MEDIA_CTRL_OBJ) | $(CLI_BUILD)
 	$(CC) $(CFLAGS) -o $@ $^
@@ -37,6 +40,9 @@ $(CLI_BUILD)/transport_cli: transport_cli.c $(COMMON_OBJ) $(SERIAL_OBJ) $(TRANSP
 $(CLI_BUILD)/discovery_cli: discovery_cli.c $(COMMON_OBJ) $(SERIAL_OBJ) $(DISCOVERY_OBJ) | $(CLI_BUILD)
 	$(CC) $(CFLAGS) -o $@ $^ -lpthread
 
+$(CLI_BUILD)/config_cli: config_cli.c $(COMMON_OBJ) $(CONFIG_OBJ) | $(CLI_BUILD)
+	$(CC) $(CFLAGS) -o $@ $^
+
 $(CLI_BUILD):
 	mkdir -p $@
 
@@ -45,4 +51,5 @@ clean:
 		$(CLI_BUILD)/media_ctrl_cli \
 		$(CLI_BUILD)/v4l2_ctrl_cli \
 		$(CLI_BUILD)/transport_cli \
-		$(CLI_BUILD)/discovery_cli
+		$(CLI_BUILD)/discovery_cli \
+		$(CLI_BUILD)/config_cli

dev/cli/config_cli.c

@@ -0,0 +1,73 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "config.h"
+#include "discovery.h"
+#include "transport.h"
+#include "error.h"
+
+/*
+ * Example schema covering node identity, discovery, and transport.
+ * Each module would normally provide its own schema table; they are
+ * combined here for the CLI demo.
+ */
+
+static const struct Config_Flag_Def function_flag_defs[] = {
+	{ "source",     DISCOVERY_FLAG_SOURCE     },
+	{ "relay",      DISCOVERY_FLAG_RELAY      },
+	{ "sink",       DISCOVERY_FLAG_SINK       },
+	{ "controller", DISCOVERY_FLAG_CONTROLLER },
+	{ NULL, 0 }
+};
+
+static const struct Config_Def schema[] = {
+	/* section       key                   type               default */
+	{ "node",       "name",               CONFIG_STRING,     "unnamed:0",  NULL              },
+	{ "node",       "site_id",            CONFIG_UINT16,     "0",          NULL              },
+	{ "node",       "tcp_port",           CONFIG_UINT16,     "8000",       NULL              },
+	{ "node",       "function",           CONFIG_FLAGS,      "source",     function_flag_defs },
+
+	{ "discovery",  "interval_ms",        CONFIG_UINT32,     "5000",       NULL              },
+	{ "discovery",  "timeout_intervals",  CONFIG_UINT32,     "3",          NULL              },
+	{ "discovery",  "connect_mask",       CONFIG_FLAGS,      "",           function_flag_defs },
+
+	{ "transport",  "max_connections",    CONFIG_UINT32,     "16",         NULL              },
+	{ "transport",  "max_payload",        CONFIG_UINT32,     "16777216",   NULL              },
+
+	{ NULL }
+};
+
+static void usage(void) {
+	fprintf(stderr,
+		"usage: config_cli <file>\n"
+		"       config_cli --defaults\n"
+		"\n"
+		"  <file>       load config file and print effective values\n"
+		"  --defaults   print schema defaults without a file\n");
+}
+
+int main(int argc, char **argv) {
+	if (argc < 2) {
+		usage();
+		return 1;
+	}
+
+	struct Config *cfg;
+	struct App_Error err;
+
+	if (argv[1][0] == '-') {
+		err = config_defaults(&cfg, schema);
+	} else {
+		err = config_load(&cfg, argv[1], schema);
+	}
+
+	if (!APP_IS_OK(err)) {
+		fprintf(stderr, "config_load: errno %d\n", err.detail.syscall.err_no);
+		return 1;
+	}
+
+	config_dump(cfg);
+
+	config_free(cfg);
+	return 0;
+}