chore: tie the DFU packet length to the shared ATT MTU and fix two stale notes

Author: jamesarich

AGENTS.md

@@ -153,10 +153,7 @@ itself; a human has to edit it too.
 
 - **ARM GCC version matters.** CI pins exactly `12.3.Rel1`; 13.3.Rel1 also
   compiles clean and is the closest verified-working version if you can't
-  get the exact CI-pinned one. GCC 15 is unverified here; Adafruit's scoped
-  `#pragma GCC diagnostic` for its `-Werror=array-bounds` false positive in
-  `lib/sdk11/components/libraries/bootloader_dfu/bootloader_settings.c`
-  (a fixed MBR-address read) is in.
+  get the exact CI-pinned one. GCC 15 is unverified here.
 - **MeshCore/Ripple content has been deliberately removed** from the docs
   (README, changelog) — this is Meshtastic's own branded fork now, not a
   place to re-add other companion-firmware documentation. If you're

lib/sdk11/components/ble/ble_services/ble_dfu/ble_dfu.c

@@ -16,8 +16,9 @@
 #include "ble_srv_common.h"
 #include <stddef.h>
 #include "sdk_common.h"
+#include "ble_dfu_cfg.h"
 
-#define MAX_DFU_PKT_LEN         (247 - 3) // MTU - 3 bytes for ATT header       /**< Maximum length (in bytes) of the DFU Packet characteristic. */
+#define MAX_DFU_PKT_LEN         (BLEGATT_ATT_MTU_MAX - 3) // MTU - 3 bytes for ATT header       /**< Maximum length (in bytes) of the DFU Packet characteristic. */
 #define PKT_START_DFU_PARAM_LEN 2                                               /**< Length (in bytes) of the parameters for Packet Start DFU Request. */
 #define PKT_INIT_DFU_PARAM_LEN  2                                               /**< Length (in bytes) of the parameters for Packet Init DFU Request. */
 #define PKT_RCPT_NOTIF_REQ_LEN  3                                               /**< Length (in bytes) of the Packet Receipt Notification Request. */

src/main.c

@@ -130,7 +130,7 @@ uint32_t* dbl_reset_mem = ((uint32_t*) DFU_DBL_RESET_MEM);
 // true if ble, false if serial
 bool _ota_dfu = false;
 bool _ota_connected = false;
-// Set after the OTA session so the app jump does not init the SoftDevice twice.
+// Set when the OTA session initializes the SoftDevice, so the app jump does not initialize it twice.
 bool _sd_inited = false;
 
 bool is_ota(void) {