feat(buzzy): add buzzy board support with SPI flash, fix build warnings

- Register BOARD_ROOT in CMakeLists.txt and sysbuild/CMakeLists.txt
- Add boardRoots to VS Code settings for board picker
- buzzy.dts: add nordic,pm-ext-flash chosen, external-flash and i2s-audio aliases
- nrf52840dk overlay: add external-flash alias (mirrors qspi-flash)
- fs_mgmt/Kconfig: select SPI_NOR for BOARD_BUZZY, NORDIC_QSPI_NOR for DK
- fs_mgmt.c: use external-flash alias instead of qspi-flash
- audio.c: bound snprintf to avoid truncation warning
- prj.conf: remove STACK_SENTINEL (conflicts with MPU_STACK_GUARD)
- mcuboot.conf: remove UART_CONSOLE (no SERIAL on buzzy)
- Delete mcuboot.overlay (no serial recovery needed)

Both buzzy/nrf52840 and nrf52840dk/nrf52840 build cleanly with zero warnings.

firmware/boards/iten/buzzy/buzzy.dts

@@ -14,6 +14,7 @@
 		zephyr,sram = &sram0;
 		zephyr,flash = &flash0;
 		zephyr,code-partition = &slot0_partition;
+		nordic,pm-ext-flash = &mx25r64;
 	};
 	
 	/* SD_MODE pin for MAX98357A power gating */
@@ -88,6 +89,7 @@
 		chg-status = &chg_status;
 		chg-fast = &chg_fast;
 		external-flash = &mx25r64;
+		i2s-audio = &i2s0;
 	};
 };
 

firmware/boards/nrf52840dk_nrf52840.overlay

@@ -3,6 +3,7 @@
         nordic,pm-ext-flash = &mx25r64;
     };
     aliases {
+        external-flash = &mx25r64;
         qspi-flash = &mx25r64;
         i2s-audio = &i2s0;
     };

firmware/libs/audio/src/audio.c

@@ -186,7 +186,8 @@ static int audio_select_random_to_buf(char *buf, size_t buf_size)
         {
             if (current_index == random_index)
             {
-                snprintf(buf, buf_size, "%s/%s", FS_AUDIO_PATH, entry.name);
+                snprintf(buf, buf_size, "%s/%.*s", FS_AUDIO_PATH,
+                         (int)(buf_size - sizeof(FS_AUDIO_PATH) - 1U), entry.name);
                 LOG_DBG("Selected random audio file: %s", buf);
                 found = true;
                 break;

firmware/libs/fs_mgmt/Kconfig

@@ -7,7 +7,9 @@ menuconfig FS_MGMT
     select FILE_SYSTEM_LITTLEFS
     select FILE_SYSTEM_MKFS
     select FLASH_PAGE_LAYOUT
-    select NORDIC_QSPI_NOR if SOC_SERIES_NRF52X && (SOC_NRF52840_QIAA || SOC_NRF52833_QIAA)
+    select SPI_NOR if BOARD_BUZZY
+    select PM_OVERRIDE_EXTERNAL_DRIVER_CHECK if BOARD_BUZZY
+    select NORDIC_QSPI_NOR if BOARD_NRF52840DK_NRF52840
     help
       Library for initializing and managing the file system.
 

firmware/libs/fs_mgmt/src/fs_mgmt.c

@@ -14,8 +14,8 @@ LOG_MODULE_REGISTER(fs_mgmt, CONFIG_FS_MGMT_LOG_LEVEL);
 #define FS_PARTITION_ID FLASH_AREA_ID(littlefs_storage)
 FS_LITTLEFS_DECLARE_DEFAULT_CONFIG(fs_storage_data);
 
-#define QSPI_FLASH_NODE DT_ALIAS(qspi_flash)
-static const struct device *flash_dev = DEVICE_DT_GET(QSPI_FLASH_NODE);
+#define EXTERNAL_FLASH_NODE DT_ALIAS(external_flash)
+static const struct device *flash_dev = DEVICE_DT_GET(EXTERNAL_FLASH_NODE);
 
 #define TAG_MAGIC "TAG!"
 #define TAG_FORMAT_VERSION 1U

firmware/prj.conf

@@ -16,4 +16,3 @@ CONFIG_PM_DEVICE=y
 CONFIG_MAIN_STACK_SIZE=2048
 CONFIG_INIT_STACKS=y
 CONFIG_THREAD_STACK_INFO=y
-CONFIG_STACK_SENTINEL=y

firmware/sysbuild/mcuboot.conf

@@ -1,6 +1,5 @@
 CONFIG_LOG=y
 # CONFIG_MCUBOOT_SERIAL=y
-CONFIG_UART_CONSOLE=y
 # CONFIG_SINGLE_APPLICATION_SLOT=n
 # CONFIG_MCUBOOT_INDICATION_LED=y
 # CONFIG_BOOT_SERIAL_CDC_ACM=y

firmware/sysbuild/mcuboot.overlay

@@ -1,13 +0,0 @@
-/ {
-  aliases {
-		mcuboot-button0 = &button0;
-		mcuboot-led0 = &led0;
-  };
-};
-
-/* Step 2.1 - Configure CDC ACM */
-&zephyr_udc0 {
-	cdc_acm_uart0: cdc_acm_uart0 {
-		compatible = "zephyr,cdc-acm-uart";
-	};
-};