docs: add embedded toolchain readiness and configuration guidance

Fix tagline to include Cortex-A. Add readiness table to README showing
all three targets are pre-installed. Add CMake toolchain file examples
to USER_GUIDE for desktop, bare-metal, and Linux cross-compilation.

Author: abitofhelp

README.md

@@ -7,7 +7,7 @@
 [![Clang](https://img.shields.io/badge/Clang-20-6f42c1)](#pre-installed-tools)
 [![Container](https://img.shields.io/badge/container-ghcr.io%2Fabitofhelp%2Fdev--container--cpp-0A66C2)](#image-names)
 
-Professional C++ development container for desktop and embedded (ARM Cortex-M) development.
+Professional C++ development container for desktop and embedded (ARM Cortex-M/A) development.
 
 ## Supported Architectures
 
@@ -185,6 +185,17 @@ The bare-metal toolchain includes OpenOCD, stlink-tools, and gdb-multiarch for
 flashing and debugging. The Linux cross-compiler includes the full sysroot
 (`libc6-dev-armhf-cross`) for building Linux userspace applications.
 
+### Embedded Toolchain Readiness
+
+Both images are fully self-contained for all three targets. No additional
+downloads or toolchain installation is required.
+
+| Target | Compiler | Status |
+|--------|----------|--------|
+| Desktop (native) | `g++` / `clang++` | Pre-installed |
+| STM32F769I — Cortex-M7 bare-metal | `arm-none-eabi-g++` | Pre-installed |
+| STM32MP135F — Cortex-A7 Linux | `arm-linux-gnueabihf-g++` | Pre-installed |
+
 ## STM32 Custom Image
 
 For projects that require ST's proprietary tools, developers can build a custom

USER_GUIDE.md

@@ -81,6 +81,64 @@ flashing and debugging. The Linux cross-compiler includes the full sysroot
 For ST's proprietary tools (STM32CubeCLT, STM32CubeMX), see the "STM32 Custom
 Image" section in [README.md](README.md#stm32-custom-image).
 
+#### Configuring your project for each target
+
+**Desktop (native)**
+
+No toolchain file is needed. Configure and build with CMake directly:
+
+```bash
+cmake -B build -G Ninja
+cmake --build build
+```
+
+**STM32F769I — Cortex-M7 bare-metal**
+
+Create a CMake toolchain file at `cmake/arm-none-eabi.cmake`:
+
+```cmake
+set(CMAKE_SYSTEM_NAME Generic)
+set(CMAKE_SYSTEM_PROCESSOR arm)
+
+set(CMAKE_C_COMPILER   arm-none-eabi-gcc)
+set(CMAKE_CXX_COMPILER arm-none-eabi-g++)
+set(CMAKE_ASM_COMPILER arm-none-eabi-gcc)
+
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+```
+
+Then configure with the toolchain file:
+
+```bash
+cmake -B build -G Ninja -DCMAKE_TOOLCHAIN_FILE=cmake/arm-none-eabi.cmake
+cmake --build build
+```
+
+**STM32MP135F — Cortex-A7 Linux**
+
+Create a CMake toolchain file at `cmake/arm-linux-gnueabihf.cmake`:
+
+```cmake
+set(CMAKE_SYSTEM_NAME Linux)
+set(CMAKE_SYSTEM_PROCESSOR arm)
+
+set(CMAKE_C_COMPILER   arm-linux-gnueabihf-gcc)
+set(CMAKE_CXX_COMPILER arm-linux-gnueabihf-g++)
+
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+```
+
+Then configure with the toolchain file:
+
+```bash
+cmake -B build -G Ninja -DCMAKE_TOOLCHAIN_FILE=cmake/arm-linux-gnueabihf.cmake
+cmake --build build
+```
+
 ---
 
 ## 1. Prerequisites