refactor: enforce max 8 code lines, add docstrings, fix warnings across all Rust and C SDK projects

Rust (all 15 projects):
- Refactored overlength functions: format_counter, format_u8, format_f32_1,
  format_u32_minimal, gpio_drive, read_sensor, poll_sensor, format_round_trip,
  format_u32, prepare_write_buf, write_min_digits, write_temp, UartDriver::init,
  init_spi, angle_to_pulse_us, compute_servo_level
- Added 200+ docstrings to test functions, mock structs, impl blocks
- Fixed pub static comments (//) to doc comments (///) in all main.rs files
- Fixed helper function ordering (helpers above callers)
- Fixed Fn(u32) -> FnMut(u32) bound in button poll_button
- Moved OneShot trait import from main.rs to board.rs in adc project
- Added unsafe {} blocks in flash unsafe fn bodies (Rust 2024 edition)
- Removed unused hal::Clock imports from pwm/servo main.rs
- All 15 projects build with zero errors and zero warnings

C Pico SDK (all 15 projects):
- Added docstrings to all public functions, macros, and static variables
- All 15 projects rebuilt with zero errors

Cleanup:
- Removed build/ and target/ directories from git tracking
- Added target/ to .gitignore
- Deleted temporary fix_rust_docs.py script

drivers/0x01_uart_rust/src/main.rs

@@ -63,13 +63,13 @@ use rp235x_hal as hal;
 #[cfg(rp2040)]
 use rp2040_hal as hal;
 
-// Second-stage boot loader for RP2040
+/// Second-stage boot loader for RP2040
 #[unsafe(link_section = ".boot2")]
 #[used]
 #[cfg(rp2040)]
 pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER_W25Q080;
 
-// Boot metadata for the RP2350 Boot ROM
+/// Boot metadata for the RP2350 Boot ROM
 #[unsafe(link_section = ".start_block")]
 #[used]
 #[cfg(rp2350)]
@@ -81,7 +81,7 @@ fn main() -> ! {
     board::run(hal::pac::Peripherals::take().unwrap())
 }
 
-// Picotool binary info metadata
+/// Picotool binary info metadata
 #[unsafe(link_section = ".bi_entries")]
 #[used]
 pub static PICOTOOL_ENTRIES: [hal::binary_info::EntryAddr; 5] = [

drivers/0x01_uart_rust/src/uart.rs

@@ -60,6 +60,14 @@ pub struct UartDriver {
     uart: EnabledUart,
 }
 
+/// Reconfigure TX and RX pins from their default state to UART function.
+fn reconfigure_pins(tx_pin: TxPinDefault, rx_pin: RxPinDefault) -> (TxPin, RxPin) {
+    (
+        tx_pin.reconfigure::<FunctionUart, PullNone>(),
+        rx_pin.reconfigure::<FunctionUart, PullNone>(),
+    )
+}
+
 impl UartDriver {
     /// Initialize hardware UART0 on the specified TX and RX GPIO pins.
     ///
@@ -86,10 +94,7 @@ impl UartDriver {
         resets: &mut hal::pac::RESETS,
         clocks: &hal::clocks::ClocksManager,
     ) -> Self {
-        let pins = (
-            tx_pin.reconfigure::<FunctionUart, PullNone>(),
-            rx_pin.reconfigure::<FunctionUart, PullNone>(),
-        );
+        let pins = reconfigure_pins(tx_pin, rx_pin);
         let cfg = UartConfig::new(baud_rate.Hz(), DataBits::Eight, None, StopBits::One);
         let uart = UartPeripheral::new(uart0, pins, resets)
             .enable(cfg, clocks.peripheral_clock.freq())
@@ -168,41 +173,49 @@ mod tests {
     // Import all parent module items
     use super::*;
 
+    /// To upper lowercase a.
     #[test]
     fn to_upper_lowercase_a() {
         assert_eq!(UartDriver::to_upper(b'a'), b'A');
     }
 
+    /// To upper lowercase z.
     #[test]
     fn to_upper_lowercase_z() {
         assert_eq!(UartDriver::to_upper(b'z'), b'Z');
     }
 
+    /// To upper lowercase m.
     #[test]
     fn to_upper_lowercase_m() {
         assert_eq!(UartDriver::to_upper(b'm'), b'M');
     }
 
+    /// To upper already uppercase.
     #[test]
     fn to_upper_already_uppercase() {
         assert_eq!(UartDriver::to_upper(b'A'), b'A');
     }
 
+    /// To upper digit unchanged.
     #[test]
     fn to_upper_digit_unchanged() {
         assert_eq!(UartDriver::to_upper(b'5'), b'5');
     }
 
+    /// To upper space unchanged.
     #[test]
     fn to_upper_space_unchanged() {
         assert_eq!(UartDriver::to_upper(b' '), b' ');
     }
 
+    /// To upper newline unchanged.
     #[test]
     fn to_upper_newline_unchanged() {
         assert_eq!(UartDriver::to_upper(b'\n'), b'\n');
     }
 
+    /// To upper null unchanged.
     #[test]
     fn to_upper_null_unchanged() {
         assert_eq!(UartDriver::to_upper(0), 0);