Migrate to Waveshare ESP32-S3-Touch-AMOLED-2.16 with auto-rotation, splash, and battery

Full hardware swap from Panlee SC01 Plus (480×320 IPS) to Waveshare 2.16"
square AMOLED (480×480, CO5300 + CST9220 + AXP2101 + QMI8658). Library
stack moves to Arduino_GFX, SensorLib, XPowersLib on the pioarduino
platform 55.03.38-1 (Arduino Core 3.x).

UI:
- 4 screens (splash, usage, controller, bluetooth) with 3-button physical
  navigation: GPIO 0 = prev, AXP PKEY = cycle, GPIO 18 = next.
- IMU-driven 90° auto-rotation. CO5300 can't rotate via MADCTL, so flush
  callback does CPU strip-rotation in PARTIAL render mode. Rotation
  transitions use AMOLED brightness flash (instant black → redraw → ramp).
- Battery indicator (Lucide icons) in upper-right, RGB565A8 alpha so it
  blends over the splash animations.
- USB plugged/unplugged auto-switches between Usage and Controller
  screens (suppressed while on splash).
- Fonts and icons re-scaled ~1.9× for the higher-DPI panel; 20px margins
  to clear rounded corners.

Splash:
- 13 × 20×20 pixel-art creature animations sourced from
  claudepix.vercel.app via tools/scrape_claudepix.js (scraper handles
  both PRESET creature-engine and standalone FRAMES+PAL formats).
  tools/convert_to_c.js emits firmware/src/splash_animations.h.
  Attribution preserved in README and the generated header.

Tooling:
- tools/png_to_lvgl.js converts alpha PNGs to LVGL RGB565A8 (planar
  layout, with --tint to colorize Lucide black-on-transparent sources).
- tools/scrape_claudepix.js, tools/convert_to_c.js for the splash
  pipeline.

Docs:
- New worktree CLAUDE.md with hardware pin map, file inventory, build
  commands, and the 8 critical gotchas (CO5300 rotation, OPI PSRAM,
  pioarduino requirement, LVGL 9 font patching, centralized touch read,
  even-aligned flush regions, touch swap/mirror values, RGB565A8 layout).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

firmware/src/imu.cpp

@@ -0,0 +1,81 @@
+#include "imu.h"
+#include "display_cfg.h"
+#include <Arduino.h>
+
+// Poll and hysteresis timing
+#define IMU_POLL_MS       100    // read accel at ~10 Hz
+#define STABLE_TIME_MS    300    // orientation must be stable this long before rotating
+#define TILT_THRESHOLD    0.5f   // ~30 degrees from axis (sin(30) ~ 0.5)
+
+static uint8_t  current_rotation = 0;
+static uint8_t  candidate_rotation = 0;
+static uint32_t candidate_since = 0;
+static uint32_t last_poll_ms = 0;
+static bool     imu_ok = false;
+
+// Determine target rotation from accelerometer gravity vector.
+// Returns 0-3 or 255 if ambiguous (e.g. face-up/face-down).
+static uint8_t accel_to_rotation(float ax, float ay) {
+    float abs_ax = fabsf(ax);
+    float abs_ay = fabsf(ay);
+
+    if (abs_ax < TILT_THRESHOLD && abs_ay < TILT_THRESHOLD) {
+        return 255;  // ambiguous, keep current
+    }
+
+    if (abs_ay > abs_ax) {
+        return (ay > 0) ? 3 : 1;
+    } else {
+        return (ax > 0) ? 0 : 2;
+    }
+}
+
+void imu_init(void) {
+    if (!imu.begin(Wire, QMI8658_L_SLAVE_ADDRESS, IIC_SDA, IIC_SCL)) {
+        Serial.println("QMI8658 init failed");
+        return;
+    }
+    Serial.println("QMI8658 init OK");
+
+    imu.configAccelerometer(
+        SensorQMI8658::ACC_RANGE_4G,
+        SensorQMI8658::ACC_ODR_LOWPOWER_21Hz,
+        SensorQMI8658::LPF_MODE_3);
+    imu.enableAccelerometer();
+
+    imu_ok = true;
+}
+
+void imu_tick(void) {
+    if (!imu_ok) return;
+
+    uint32_t now = millis();
+    if (now - last_poll_ms < IMU_POLL_MS) return;
+    last_poll_ms = now;
+
+    float ax, ay, az;
+    if (!imu.getAccelerometer(ax, ay, az)) return;
+
+    uint8_t target = accel_to_rotation(ax, ay);
+    if (target == 255 || target == current_rotation) {
+        candidate_rotation = current_rotation;
+        return;
+    }
+
+    if (target != candidate_rotation) {
+        candidate_rotation = target;
+        candidate_since = now;
+    } else if (now - candidate_since >= STABLE_TIME_MS) {
+        current_rotation = target;
+        Serial.printf("Rotation: %d\n", current_rotation);
+    }
+}
+
+uint8_t imu_get_rotation(void) {
+    return current_rotation;
+}
+
+void imu_set_rotation(uint8_t r) {
+    current_rotation = r % 4;
+    Serial.printf("Rotation: %d (manual)\n", current_rotation);
+}