Add stable CYD firmware, USB calibration wizard and complete setup guide

diagnostics/capture_serial.py

@@ -0,0 +1,19 @@
+"""Capture ESP32 boot/runtime diagnostics. Requires pyserial (in ESPHome's venv)."""
+import argparse
+import time
+import serial
+
+parser = argparse.ArgumentParser()
+parser.add_argument('--port', default='/dev/cu.usbserial-130')
+parser.add_argument('--seconds', type=int, default=90)
+parser.add_argument('--reset', action='store_true')
+args = parser.parse_args()
+with serial.Serial(args.port, 115200, timeout=0.2) as port:
+    if args.reset:
+        port.dtr = False
+        port.rts = True
+        time.sleep(0.1)
+        port.rts = False
+    end = time.monotonic() + args.seconds
+    while time.monotonic() < end:
+        print(port.read(4096).decode('utf-8', errors='replace'), end='', flush=True)