Fix implicit decl of emit_feature_state in adaptive_controller

fast_loop_cb calls emit_feature_state() at line 224, but the static
definition is at line 256. GCC treats the implicit declaration as
non-static, then the real static definition conflicts, and
-Werror=all promotes both to hard build errors.

Add a forward declaration above the first use. Unblocks ESP32-S3
firmware build and all QEMU matrix jobs.

Co-Authored-By: claude-flow <ruv@ruv.net>

firmware/esp32-csi-node/main/adaptive_controller.c

@@ -43,6 +43,9 @@ static TimerHandle_t s_fast_timer   = NULL;
 static TimerHandle_t s_medium_timer = NULL;
 static TimerHandle_t s_slow_timer   = NULL;
 
+/* Forward decl: defined below, called from fast_loop_cb. */
+static void emit_feature_state(void);
+
 /* ---- Defaults ---- */
 
 #ifndef CONFIG_ADAPTIVE_FAST_LOOP_MS