fix(firmware): capture DATA frames on display-less boards — #893/#866/#897

The pre-built binaries set a MGMT-only promiscuous filter
(WIFI_PROMIS_FILTER_MASK_MGMT) as the #396 workaround — DATA-frame
interrupt load races the QSPI display's SPI traffic against the SPI-flash
cache and crashes Core 0 in wDev_ProcessFiq. But MGMT-only fires the CSI
callback only on sparse management frames, so on the common DISPLAY-LESS
boards (DevKitC-1, T7-S3, N8R8) CSI yield collapses to 0 pps under real
traffic (#521) — the node looks dead despite being on the network, which
is the root cause of most "can't reproduce / it's fake" reports (#804/#37).

A board with no AMOLED panel has no QSPI/SPI-flash contention, so it can
safely capture DATA frames. After the boot-time display probe runs:
  - display present  -> keep MGMT-only (preserve #396 crash protection)
  - no display       -> upgrade filter to MGMT|DATA (restore CSI yield)

Implementation (runtime-gated, no boot reorder):
  - display_task.c: s_display_active flag + display_is_active() accessor,
    set true only when the panel is detected and the display task starts.
  - csi_collector.c: csi_collector_enable_data_capture() re-sets the
    promiscuous filter to MGMT|DATA.
  - main.c: after display_task_start(), if !display_is_active() (or display
    support not compiled in), upgrade the filter.

Build-verified on BOTH targets: esp32c6 (headless path) and esp32s3
(display path, display_task.c compiled) — Project build complete, RC 0.
Needs on-hardware confirmation that yield recovers and no #396 crash.

firmware/esp32-csi-node/main/display_task.h

@@ -7,6 +7,7 @@
 #define DISPLAY_TASK_H
 
 #include "esp_err.h"
+#include <stdbool.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -22,6 +23,15 @@ extern "C" {
  */
 esp_err_t display_task_start(void);
 
+/**
+ * @return true once an AMOLED panel has been detected and the display task
+ * is running; false on headless boards (no panel, or built without display
+ * support). Used to choose the CSI promiscuous filter (RuView#893): a board
+ * with no display has no QSPI/SPI-flash contention, so it can safely capture
+ * DATA frames for proper CSI yield instead of starving on MGMT-only.
+ */
+bool display_is_active(void);
+
 #ifdef __cplusplus
 }
 #endif