feat(01-01): LED driver — dual strip initialization and output

- led_driver.h declares StripWand (NeoGrbwFeature/RMT) + StripSchrank (NeoWs2801Spi2MhzMethod)
- led_driver.cpp implements initStrips, showBothStrips, setAllWand/Schrank, applyBrightness helpers
- showBothStrips calls stripWand.Show() first (non-blocking DMA) then stripSchrank.Show() (blocking SPI)
- Brightness clamped to [0.0f, BRIGHTNESS_MAX] before scaling

firmware/src/led_driver.cpp

@@ -0,0 +1,59 @@
+#include "led_driver.h"
+#include <Arduino.h>
+#include <algorithm>
+
+// Strip object definitions
+// StripWand: SK6812 RGBW via RMT (DMA, non-blocking transfer)
+StripWand    stripWand(LED_COUNT_WAND, PIN_SK6812);
+// StripSchrank: WS2801 RGB via hardware SPI at 2MHz (no pin arg — uses hardware SPI pins)
+StripSchrank stripSchrank(LED_COUNT_SCHRANK);
+
+void initStrips() {
+    stripWand.Begin();
+    stripSchrank.Begin();
+
+    // Clear both strips to off on startup
+    stripWand.ClearTo(RgbwColor(0, 0, 0, 0));
+    stripSchrank.ClearTo(RgbColor(0, 0, 0));
+
+    showBothStrips();
+
+    Serial.println("LED driver: Wand 300 RGBW (SK6812 RMT), Schrank 160 RGB (WS2801 SPI 2MHz)");
+}
+
+void showBothStrips() {
+    // RMT DMA runs concurrently; both strips finish in ~10ms window
+    stripWand.Show();     // Start non-blocking DMA transfer first
+    stripSchrank.Show();  // Blocks ~4ms (480 bytes at 2MHz); RMT DMA runs in parallel
+}
+
+RgbwColor applyBrightnessW(RgbwColor c, float factor) {
+    // Clamp factor to [0.0f, BRIGHTNESS_MAX] before scaling
+    factor = std::max(0.0f, std::min(factor, BRIGHTNESS_MAX));
+    return RgbwColor(
+        static_cast<uint8_t>(c.R * factor),
+        static_cast<uint8_t>(c.G * factor),
+        static_cast<uint8_t>(c.B * factor),
+        static_cast<uint8_t>(c.W * factor)
+    );
+}
+
+RgbColor applyBrightnessR(RgbColor c, float factor) {
+    // Clamp factor to [0.0f, BRIGHTNESS_MAX] before scaling
+    factor = std::max(0.0f, std::min(factor, BRIGHTNESS_MAX));
+    return RgbColor(
+        static_cast<uint8_t>(c.R * factor),
+        static_cast<uint8_t>(c.G * factor),
+        static_cast<uint8_t>(c.B * factor)
+    );
+}
+
+void setAllWand(RgbwColor color) {
+    // NeoPixelBus ClearTo fills the entire strip with the given color
+    stripWand.ClearTo(color);
+}
+
+void setAllSchrank(RgbColor color) {
+    // NeoPixelBus ClearTo fills the entire strip with the given color
+    stripSchrank.ClearTo(color);
+}

firmware/src/led_driver.h

@@ -0,0 +1,18 @@
+#pragma once
+#include <NeoPixelBus.h>
+#include "config.h"
+
+// SK6812: RGBW (4 bytes/LED) — MUST use NeoGrbwFeature, never NeoRgbFeature
+using StripWand    = NeoPixelBus<NeoGrbwFeature, NeoEsp32Rmt0Ws2812xMethod>;
+// WS2801: RGB (3 bytes/LED), 2MHz SPI for cable-safe 5m run
+using StripSchrank = NeoPixelBus<NeoRgbFeature, NeoWs2801Spi2MhzMethod>;
+
+extern StripWand    stripWand;
+extern StripSchrank stripSchrank;
+
+void initStrips();
+void showBothStrips();
+void setAllWand(RgbwColor color);
+void setAllSchrank(RgbColor color);
+RgbwColor applyBrightnessW(RgbwColor c, float factor);
+RgbColor  applyBrightnessR(RgbColor c, float factor);