Add Waveshare ESP32-S3-Touch-AMOLED-1.8 (368×448) board support

Port the firmware to a second Waveshare AMOLED board variant alongside
the original 2.16" / 480×480. Selection is at build time via a board
macro; both envs continue to build and flash independently.

Hardware delta vs AMOLED-2.16:
  * Display: SH8601 QSPI (vs CO5300), 368×448 portrait (vs 480² square),
    SCLK on GPIO 11 (vs 38), RST routed through an XCA9554 I/O expander
    (vs direct GPIO).
  * Touch: FT3168 @ 0x38 (vs CST9220 @ 0x5A). Driven by a ~30-line
    inline FocalTech-protocol reader in main.cpp — Waveshare's
    Arduino_DriveBus library is GPLv3 and would force the project's
    license, which the README explicitly avoids.
  * I/O expander: new XCA9554/PCA9554 @ I2C 0x20 gates LCD_RST, TP_RST,
    audio amp enable, and the PWR button. Wrapped in io_expander.{h,cpp}.
    Must initialize BEFORE display/touch or both stay in reset.
  * PMU + IMU: same AXP2101 + QMI8658 as 2.16, so power.cpp/imu.cpp
    largely reuse. IMU is initialized for I2C bus health but rotation
    is fixed at 0° (the portrait panel doesn't benefit from auto-rotate
    and the strip-rotation CPU path is excluded entirely).
  * Buttons: only BOOT (GPIO 0) is a direct GPIO; PWR is read via
    XCA9554 EXIO4 polling. No third button — the AMOLED-2.16's
    Shift+Tab key (GPIO 18) is dropped for this board.
  * Flash: 16MB (vs 8MB), partition table set to default_16MB.csv.

Code structure:
  * display_cfg.h hosts a #ifdef BOARD_AMOLED_18 / #else / #endif split
    with a PlatformDisplay typedef so call sites elsewhere stay clean.
  * main.cpp, power.cpp, ui.cpp, splash.cpp gate board-specific bits on
    the same macro. Layout constants (panel heights, content Y, font
    choices on the Bluetooth screen) compress for the 368×448 portrait
    footprint so two usage panels + bottom animation label fit without
    horizontal overflow.
  * Splash scales the 20×20 pixel-art grid to 360×360 (CELL=18 vs 24)
    and centers in the portrait canvas.
  * Old AMOLED-2.16 env is unchanged at the source level (gated under
    #ifndef BOARD_AMOLED_18) and continues to compile + flash on the
    original hardware.

CLAUDE.md updated with the two-board pin maps, build/flash commands
for both envs (macOS + Linux device paths), and the per-board gotchas.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

firmware/platformio.ini

@@ -7,6 +7,7 @@ upload_speed = 921600
 monitor_speed = 115200
 
 build_flags =
+    -DBOARD_AMOLED_216
     -DARDUINO_USB_CDC_ON_BOOT=1
     -DBOARD_HAS_PSRAM
     ; AXP2101 PMU
@@ -42,3 +43,55 @@ lib_deps =
     lvgl/lvgl@^9.2.0
     bblanchon/ArduinoJson@^7.0.0
     h2zero/NimBLE-Arduino@^2.1.1
+
+
+[env:waveshare_amoled_18]
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/55.03.38-1/platform-espressif32.zip
+board = esp32-s3-devkitc-1
+framework = arduino
+board_build.arduino.memory_type = qio_opi
+board_upload.flash_size = 16MB
+board_upload.maximum_size = 16777216
+board_build.partitions = default_16MB.csv
+upload_speed = 921600
+monitor_speed = 115200
+
+build_flags =
+    -DBOARD_AMOLED_18
+    -DARDUINO_USB_CDC_ON_BOOT=1
+    -DBOARD_HAS_PSRAM
+    ; AXP2101 PMU is present on the AMOLED-1.8 board too (battery is optional kit add-on)
+    -DXPOWERS_CHIP_AXP2101
+    ; NimBLE config — peripheral, 2 simultaneous connections so the OS can
+    ; hold the HID link (Space key from BOOT button) while the daemon holds
+    ; its own connection for the custom data service.
+    -DCONFIG_BT_NIMBLE_ROLE_BROADCASTER=1
+    -DCONFIG_BT_NIMBLE_ROLE_PERIPHERAL=1
+    -DCONFIG_BT_NIMBLE_ROLE_CENTRAL=0
+    -DCONFIG_BT_NIMBLE_ROLE_OBSERVER=0
+    -DCONFIG_BT_NIMBLE_MAX_CONNECTIONS=2
+    ; LVGL config via build flags
+    -DLV_CONF_SKIP
+    -DLV_COLOR_DEPTH=16
+    -DLV_USE_LOG=0
+    -DLV_USE_BAR=1
+    -DLV_USE_LABEL=1
+    -DLV_USE_ARC=1
+    -DLV_USE_BTN=1
+    -DLV_USE_LINE=1
+    -DLV_USE_OBJ=1
+    -DLV_USE_IMG=1
+    -DLV_USE_IMAGE=1
+    -DLV_USE_ANIMIMG=0
+    -DLV_TICK_CUSTOM=1
+    -DLV_USE_SNAPSHOT=1
+
+lib_deps =
+    ; 1.6.4+ ships Arduino_SH8601 in mainline
+    moononournation/GFX Library for Arduino@^1.6.4
+    ; SensorLib still used for QMI8658 IMU on AMOLED-1.8
+    lewisxhe/SensorLib@^0.2.6
+    lewisxhe/XPowersLib@^0.2.7
+    lvgl/lvgl@^9.2.0
+    bblanchon/ArduinoJson@^7.0.0
+    h2zero/NimBLE-Arduino@^2.1.1