Add LILYGO T-Deck Pro (ESP32-S3FN16R8) build and OpenOCD flash support

[Copilot]

The project only supported ARM STM32 targets. This adds full build and OpenOCD flash support for the LILYGO T-Deck Pro — ESP32-S3FN16R8 (Xtensa LX7 dual-core, 240 MHz, 16 MB flash, 8 MB PSRAM) with built-in USB JTAG.

New architecture: xtensa/lx7

• configs/arch/xtensa/arch.ld — elf32-xtensa-le output format
• configs/arch/xtensa/cfg.cmake — sets DMBOOT_OBJCOPY_OUTPUT_FORMAT / DMBOOT_OBJCOPY_BINARY_ARCH for Xtensa
• configs/arch/xtensa/lx7/tools-cfg.cmake — local toolchain override (checked before dmod submodule); configures xtensa-esp32s3-elf-*, enables -mabi=call0 -mlongcalls

New MCU: ESP32S3 / esp32s3fn16r8

• configs/mcu/ESP32S3.cmake — 240 MHz, OpenOCD via esp_usb_jtag.cfg + esp32s3.cfg
• configs/mcu/esp32s3/esp32s3fn16r8/mcu.ld — code in IRAM (0x40374000, 320 KB), data in DRAM (0x3FC88000, 416 KB); no ROM-bootloader cache setup required for direct JTAG load

New board: t-deck-pro

• configs/board/t-deck-pro/board.cmake — sets TARGET=ESP32S3

Startup code: Xtensa LX7

• src/arch/xtensa/lx7/startup.S — reset handler in call0 ABI: disables interrupts (rsil), initialises .data/.bss, calls low_level_init_0/1 then main()
• src/arch/xtensa/dmod_critical.c — nested critical sections via rsil/wsr PS

Build system changes

• configs/arch/armv7/cfg.cmake — now explicitly sets DMBOOT_OBJCOPY_OUTPUT_FORMAT=elf32-littlearm (previously implicit)
• scripts/embed_binary.cmake, scripts/romfs.cmake, CMakeLists.txt — replace hard-coded elf32-littlearm/arm objcopy args with the arch-aware variables
• CMakeLists.txt — checks for a local configs/arch/<arch>/<family>/tools-cfg.cmake before falling back to the dmod submodule, enabling the Xtensa toolchain to be configured without touching the submodule

Usage

cmake -DBOARD=t-deck-pro -S . -B build
cmake --build build

# Flash via built-in USB JTAG (requires Espressif OpenOCD fork)
cmake --build build --target install-firmware