Make controller input best-effort and harden OTA rollback.

Accel/tap use fire-and-forget ESP-NOW with a 10 ms FreeRTOS-safe cadence, OTA recovers from seq gaps and auto-reboots after success, and bootloader app rollback confirms after a stable boot.

Co-authored-by: Cursor <cursoragent@cursor.com>

main/ota_uart.h

@@ -45,7 +45,9 @@ void ota_uart_abort(void);
 
 /**
  * Append up to 200 bytes with strict seq checking (0, 1, 2, …).
- * Duplicates (seq < expected) return OTA_FEED_SEQ_DUP; gaps return OTA_FEED_SEQ_GAP.
+ * Duplicates (seq < expected) return OTA_FEED_SEQ_DUP.
+ * Gaps (seq > expected) return OTA_FEED_SEQ_GAP without consuming — caller
+ * should keep the session so the host can retry the current flash block.
  */
 ota_feed_result_t ota_uart_feed_chunk(uint32_t seq, const uint8_t *data, size_t len);