Add multi-panel Pico UDP firmware and Python LED control.

Pico panels get static IPs on 10.1.1.10–14 with per-panel LED counts, Makefile deploy targets, and Python examples for animations, sync tests, and direct Pi SPI control.

Co-authored-by: Cursor <cursoragent@cursor.com>

leds/detect.py

@@ -0,0 +1,64 @@
+"""Raspberry Pi model detection for choosing a WS2812 backend."""
+
+from __future__ import annotations
+
+from functools import lru_cache
+
+
+@lru_cache(maxsize=1)
+def board_model() -> str:
+    try:
+        with open("/proc/device-tree/model", "rb") as f:
+            return f.read().rstrip(b"\x00").decode("ascii")
+    except OSError:
+        return "Unknown"
+
+
+@lru_cache(maxsize=1)
+def board_family() -> str:
+    model = board_model().lower()
+    if "raspberry pi 5" in model:
+        return "pi5"
+    if "raspberry pi 4" in model:
+        return "pi4"
+    if "zero 2" in model:
+        return "pi_zero2"
+    if "zero" in model:
+        return "pi_zero"
+    if "raspberry pi 3" in model:
+        return "pi3"
+    return "unknown"
+
+
+def supports_ws281x() -> bool:
+    return board_family() != "pi5"
+
+
+def pio_device(index: int = 0) -> str | None:
+    from pathlib import Path
+
+    path = Path(f"/dev/leds{index}")
+    return str(path) if path.exists() else None
+
+
+def pio_available() -> bool:
+    return pio_device(0) is not None
+
+
+def pi5_second_spi_bus() -> int:
+    """
+    Second strip on Pi 5 SPI — prefer spi1 from dtoverlay=spi1-3cs
+    (/dev/spidev1.0, MOSI on GPIO 20). Falls back to built-in spidev10.0.
+    """
+    from pathlib import Path
+
+    if Path("/dev/spidev1.0").exists():
+        return 1
+    if Path("/dev/spidev10.0").exists():
+        return 10
+    raise RuntimeError(
+        "No second SPI device found. Add to /boot/firmware/config.txt under [all]:\n"
+        "  dtoverlay=spi1-3cs\n"
+        "Then reboot. Wire strip 1 DIN to GPIO 20 (SPI1 MOSI).\n"
+        "Note: dtparam=spi1=on is ignored on Pi 5; use the overlay in [all], not [cm5]."
+    )