Move the Nano link to Serial2, update READMEs

- ESP32 talks to the Nano on UART2 (GPIO 17 TX / GPIO 16 RX); Serial (USB)
  is now free for debug output and boot messages no longer reach the Nano
- README: wiring table, actual schedule (clock from 08:00), TODO section
  for the rewiring

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/esp32/README.md

@@ -3,8 +3,9 @@
 PlatformIO environments: `esp32` (OTA) and `esp32_usb` (USB)
 
 The ESP32 decides what is shown on the display. It never touches the panel itself. The
-BROSE9323 driver is built with `-D ESPSERIAL`, so every GFX call is sent over `Serial`
-(115200 baud) to the Nano.
+BROSE9323 driver is built with `-D ESPSERIAL`, so every GFX call is sent to the Nano over
+`Serial2` (UART2, GPIO 17 TX / GPIO 16 RX, 115200 baud). `Serial` (USB) is only used for
+debug output. Wiring is described in the [main README](../../README.md#wiring-between-esp32-and-nano).
 
 ## Files
 
@@ -40,10 +41,10 @@ BROSE9323 driver is built with `-D ESPSERIAL`, so every GFX call is sent over `S
 
 | Time | Display |
 |------|---------|
-| 07:00 – 17:00 | Pikachu and the clock, updated every minute |
+| 08:00 – 17:00 | Pikachu and the clock, updated every minute |
 | 17:00 – 22:00 | Yawning Pikachu and the clock |
-| 22:00 – 23:30 | Clock drawn only on the quarter hour; power is off in between |
-| night | Screen cleared, power off |
+| 22:00 – 23:30 | Clock shown only during the minutes :00, :15, :30 and :45; power is off in between |
+| 23:31 – 08:00 | Screen cleared, power off |
 
 ## Adding bitmaps