refactor: convert 0x01_uart_cbm and 0x02_blink_cbm to bare-metal Inc/Src structure

- Restructure flat files into Inc/ (headers) and Src/ (sources)
- Replace constants.h with rp2350.h register layer (datasheet-verified)
- Add full Doxygen docstrings on all files, functions, and structs
- Replace build.bat/clean.bat with cross-platform Makefile
- Fix GPIO_IN offset (0x004), XOSC COUNT offset (0x10), SRAM size (520K)
- Rename blink_* API to led_* (name after peripheral, not feature)
- Build outputs to build/ directory
- Cross-platform .vscode configs (Windows/macOS/Linux)

drivers/0x01_uart_cbm/linker.ld

@@ -1,44 +1,43 @@
 /**
- * @file linker.ld
- * @brief Minimal linker script for bare-metal RP2350 development
- * @author Kevin Thomas
- * @date 2025
- *
- * MIT License
- *
- * Copyright (c) 2025 Kevin Thomas
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- */
+  ******************************************************************************
+  * @file    linker.ld
+  * @author  Kevin Thomas
+  * @brief   Minimal linker script for bare-metal RP2350 development.
+  *
+  *          Defines FLASH (XIP 32 MB) and RAM (520 kB SRAM) regions.
+  *          The vector table is placed at the start of flash (0x10000000).
+  *
+  ******************************************************************************
+  * @attention
+  *
+  * Copyright (c) 2026 Kevin Thomas.
+  * All rights reserved.
+  *
+  * This software is licensed under terms that can be found in the LICENSE file
+  * in the root directory of this software component.
+  * If no LICENSE file comes with this software, it is provided AS-IS.
+  *
+  ******************************************************************************
+  */
 
+/**
+  * Entry point.
+  */
 ENTRY(Reset_Handler)
 
 /**
- * Define memory regions.
- */
+  * Define memory regions.
+  */
 __XIP_BASE   = 0x10000000;
 __XIP_SIZE   = 32M;
 
 __SRAM_BASE  = 0x20000000;
-__SRAM_SIZE  = 512K;
+__SRAM_SIZE  = 520K;
 __STACK_SIZE = 32K;
 
+/**
+  * Memory layout.
+  */
 MEMORY
 {
   RAM   (rwx) : ORIGIN = __SRAM_BASE, LENGTH = __SRAM_SIZE
@@ -46,34 +45,37 @@ MEMORY
 }
 
 /**
- * Program headers.
- */
+  * Program headers.
+  */
 PHDRS
 {
   text PT_LOAD FLAGS(5);
 }
 
 /**
- * Section placement.
- */
+  * Section placement.
+  */
 SECTIONS
 {
   . = ORIGIN(FLASH);
 
   /**
-   * Vector table MUST be first at 0x10000000.
-   */
+    * Vector table MUST be first at 0x10000000.
+    */
   .vectors :
   {
     KEEP(*(.vectors))
   } > FLASH :text
 
+  /**
+    * Verify vector table placement.
+    */
   ASSERT((ADDR(.vectors) == ORIGIN(FLASH)),
          "Vector table must be at start of flash (0x10000000)")
 
   /**
-   * Text and read-only data.
-   */
+    * Text and read-only data.
+    */
   .text :
   {
     . = ALIGN(4);
@@ -85,22 +87,28 @@ SECTIONS
   } > FLASH :text
 
   /**
-   * IMAGE_DEF block at end of code.
-   */
+    * IMAGE_DEF block at end of code.
+    */
   .embedded_block :
   {
     KEEP(*(.embedded_block))
   } > FLASH :text
 
   /**
-   * Non-secure stack symbols.
-   */
+    * Non-secure stack symbols.
+    */
   __StackTop   = ORIGIN(RAM) + LENGTH(RAM);
   __StackLimit = __StackTop - __STACK_SIZE;
   __stack      = __StackTop;
   _stack_top   = __StackTop;
 
+  /**
+    * Stack section (no load).
+    */
   .stack (NOLOAD) : { . = ALIGN(8); } > RAM
 
+  /**
+    * Provide vector table symbol to startup code.
+    */
   PROVIDE(__Vectors = ADDR(.vectors));
 }