feat(01-01): main.cpp — WiFi init, WIFI_PS_NONE, startup animation, coexistence test

- main.cpp: setup() initializes strips, shows green (connecting) then white (connected)
- esp_wifi_set_ps(WIFI_PS_NONE) called immediately after WiFi connects for RMT coexistence
- loop() toggles LED colors every 5s to confirm strip responsiveness
- Coexistence test procedure documented as comment block in main.cpp
- firmware/.gitignore excludes .pio/ and credentials.h

firmware/.gitignore

@@ -0,0 +1,2 @@
+.pio/
+credentials.h

firmware/src/main.cpp

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+#include <Arduino.h>
+#include <WiFi.h>
+#include <esp_wifi.h>
+#include "config.h"
+#include "led_driver.h"
+#include "credentials.h"
+
+// ---------------------------------------------------------------------------
+// Color constants for startup indicators
+// ---------------------------------------------------------------------------
+static const RgbwColor COLOR_STARTUP_GREEN = RgbwColor(0, 30, 0, 0);  // Dim green: WiFi connecting
+static const RgbwColor COLOR_WIFI_READY    = RgbwColor(0, 0, 0, 20);  // Dim white: WiFi connected
+static const RgbwColor COLOR_LOOP_RED      = RgbwColor(15, 0, 0, 0);  // Dim red: loop toggle A
+static const RgbwColor COLOR_LOOP_BLUE     = RgbwColor(0, 0, 15, 0);  // Dim blue: loop toggle B
+
+// ---------------------------------------------------------------------------
+// State
+// ---------------------------------------------------------------------------
+static uint32_t lastLoopTick = 0;
+static bool     loopColorToggle = false;
+
+// ---------------------------------------------------------------------------
+// WiFi connect with timeout
+// ---------------------------------------------------------------------------
+static bool connectWiFi() {
+    WiFi.begin(WIFI_SSID, WIFI_PASS);
+
+    uint32_t startMs = millis();
+    Serial.print("WiFi connecting");
+
+    while (WiFi.status() != WL_CONNECTED) {
+        if (millis() - startMs > 30000) {
+            Serial.println();
+            Serial.println("WiFi timeout — check credentials.h");
+            return false;
+        }
+        delay(500);
+        Serial.print(".");
+    }
+
+    Serial.println();
+    return true;
+}
+
+// ---------------------------------------------------------------------------
+// setup()
+// ---------------------------------------------------------------------------
+void setup() {
+    // 1. Serial — wait up to 2s for monitor to attach (USB CDC)
+    Serial.begin(115200);
+    uint32_t t0 = millis();
+    while (!Serial && millis() - t0 < 2000) { delay(10); }
+
+    Serial.println("=== LED Sync Studio — ESP32-C3 SuperMini ===");
+
+    // 2. Initialize LED strips (clears both, prints driver info)
+    initStrips();
+
+    // 3. Startup indicator: dim green = WiFi connecting
+    setAllWand(COLOR_STARTUP_GREEN);
+    showBothStrips();
+
+    // 4. Connect to WiFi
+    if (!connectWiFi()) {
+        // Stay in error state — strip stays green, serial shows timeout
+        // Developer must check credentials.h and reflash
+        return;
+    }
+
+    // 5. CRITICAL: Disable WiFi power save immediately after connect
+    //    Must be called before any LED output to prevent RMT interrupt corruption
+    esp_wifi_set_ps(WIFI_PS_NONE);
+    Serial.println("WIFI_PS_NONE set — RMT coexistence mode active");
+
+    // 6. Print connection info
+    Serial.print("WiFi connected: ");
+    Serial.println(WiFi.localIP().toString());
+
+    // 7. WiFi connected indicator: dim white
+    setAllWand(COLOR_WIFI_READY);
+    showBothStrips();
+
+    lastLoopTick = millis();
+}
+
+// ---------------------------------------------------------------------------
+// loop() — static color test: toggle strip every 5s to confirm responsiveness
+// ---------------------------------------------------------------------------
+void loop() {
+    uint32_t now = millis();
+
+    if (now - lastLoopTick >= 5000) {
+        lastLoopTick = now;
+
+        if (loopColorToggle) {
+            setAllWand(COLOR_LOOP_RED);
+        } else {
+            setAllWand(COLOR_LOOP_BLUE);
+        }
+        showBothStrips();
+
+        loopColorToggle = !loopColorToggle;
+        Serial.println("loop tick");
+    }
+}
+
+// ---------------------------------------------------------------------------
+// COEXISTENCE TEST PROCEDURE (run on day 1 before Plan 02):
+// 1. Flash firmware, open serial monitor at 115200
+// 2. Confirm: "WIFI_PS_NONE set" + IP address printed
+// 3. From Pi/laptop: run `for i in $(seq 1 300); do echo '{"v":1,"cmd":"test"}' | nc -u <ESP_IP> 4210; sleep 0.1; done`
+// 4. Observe SK6812 strip for 30 seconds during UDP burst
+// 5. PASS: Zero visible flicker throughout
+// 6. FAIL: Any flicker -> check DMA buffer size, confirm WIFI_PS_NONE, try core 2.0.17 fallback
+// ---------------------------------------------------------------------------