fix: remove duplicate docstrings from public functions in .c files

Public function docstrings belong exclusively in .h headers per
coding convention. Only static helper functions and static variables
retain docstrings in .c files. Removed 413 duplicate docstrings
across 185 files (15 CBM + 15 C SDK projects). All 30 projects
rebuild with zero errors.

drivers/0x0d_timer/timer.c

@@ -50,17 +50,6 @@ static bool _timer_shim(repeating_timer_t *rt) {
     return false;
 }
 
-/**
- * @brief Start a repeating hardware timer that fires the given callback
- *
- * Schedules callback to be invoked every period_ms milliseconds using
- * the Pico SDK add_repeating_timer_ms() API. The timer continues firing
- * until timer_driver_cancel() is called.
- *
- * @param period_ms Interval between callbacks in milliseconds (positive value)
- * @param callback  Function to call on each timer expiry; must return true to
- *                  continue repeating, false to stop
- */
 void timer_driver_start(int32_t period_ms, timer_driver_callback_t callback) {
     if (g_timer_active) {
         cancel_repeating_timer(&g_timer);
@@ -70,12 +59,6 @@ void timer_driver_start(int32_t period_ms, timer_driver_callback_t callback) {
     g_timer_active = add_repeating_timer_ms(period_ms, _timer_shim, NULL, &g_timer);
 }
 
-/**
- * @brief Cancel the active repeating timer
- *
- * Stops the timer started by timer_driver_start(). Safe to call even if the
- * timer has already fired and self-cancelled.
- */
 void timer_driver_cancel(void) {
     if (!g_timer_active)
         return;