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/0x02_blink_rust/src/blink.rs

@@ -103,50 +103,62 @@ mod tests {
     // Error type trait for mock pin implementations
     use embedded_hal::digital::ErrorType;
 
+    /// Mock GPIO pin for testing.
     struct MockPin {
         state: bool,
     }
 
     impl MockPin {
+        /// New.
         fn new() -> Self {
             Self { state: false }
         }
     }
 
+    /// ErrorType implementation for MockPin.
     impl ErrorType for MockPin {
         type Error = Infallible;
     }
 
+    /// OutputPin implementation for MockPin.
     impl OutputPin for MockPin {
+        /// Set low.
         fn set_low(&mut self) -> Result<(), Self::Error> {
             self.state = false;
             Ok(())
         }
+        /// Set high.
         fn set_high(&mut self) -> Result<(), Self::Error> {
             self.state = true;
             Ok(())
         }
     }
 
+    /// StatefulOutputPin implementation for MockPin.
     impl StatefulOutputPin for MockPin {
+        /// Is set high.
         fn is_set_high(&mut self) -> Result<bool, Self::Error> {
             Ok(self.state)
         }
+        /// Is set low.
         fn is_set_low(&mut self) -> Result<bool, Self::Error> {
             Ok(!self.state)
         }
+        /// Toggle.
         fn toggle(&mut self) -> Result<(), Self::Error> {
             self.state = !self.state;
             Ok(())
         }
     }
 
+    /// Init starts low.
     #[test]
     fn init_starts_low() {
         let drv = BlinkDriver::init(MockPin::new());
         assert!(!drv.pin.state);
     }
 
+    /// On sets high.
     #[test]
     fn on_sets_high() {
         let mut drv = BlinkDriver::init(MockPin::new());
@@ -154,6 +166,7 @@ mod tests {
         assert!(drv.pin.state);
     }
 
+    /// Off sets low.
     #[test]
     fn off_sets_low() {
         let mut drv = BlinkDriver::init(MockPin::new());
@@ -162,6 +175,7 @@ mod tests {
         assert!(!drv.pin.state);
     }
 
+    /// Toggle from low goes high.
     #[test]
     fn toggle_from_low_goes_high() {
         let mut drv = BlinkDriver::init(MockPin::new());
@@ -169,6 +183,7 @@ mod tests {
         assert!(drv.pin.state);
     }
 
+    /// Toggle from high goes low.
     #[test]
     fn toggle_from_high_goes_low() {
         let mut drv = BlinkDriver::init(MockPin::new());
@@ -177,6 +192,7 @@ mod tests {
         assert!(!drv.pin.state);
     }
 
+    /// Get state reflects on.
     #[test]
     fn get_state_reflects_on() {
         let mut drv = BlinkDriver::init(MockPin::new());
@@ -184,6 +200,7 @@ mod tests {
         assert!(drv.get_state());
     }
 
+    /// Get state reflects off.
     #[test]
     fn get_state_reflects_off() {
         let mut drv = BlinkDriver::init(MockPin::new());
@@ -192,6 +209,7 @@ mod tests {
         assert!(!drv.get_state());
     }
 
+    /// Double toggle returns to original.
     #[test]
     fn double_toggle_returns_to_original() {
         let mut drv = BlinkDriver::init(MockPin::new());

drivers/0x02_blink_rust/src/main.rs

@@ -61,13 +61,13 @@ 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)]
@@ -79,7 +79,7 @@ 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] = [