feat(espnow): Pi bridge client, binary wire, and espnow-sender firmware

Replace serial/Wi-Fi driver transport paths with WebSocket bridge client,
binary espnow_wire delivery, device announce registry, and restructured
espnow-sender (AP + broadcast passthrough). Includes docs and tests.

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

src/util/binary_driver_messages.py

@@ -0,0 +1,62 @@
+"""Build binary ESP-NOW CMD / GROUP_CMD packets from preset/select data."""
+
+from __future__ import annotations
+
+from typing import Any, Dict, List, Optional
+
+from util.binary_envelope import pack_binary_envelope_v2
+from util.espnow_wire import MAX_ESPNOW_PAYLOAD, pack_cmd, pack_group_cmd
+
+
+def v1_dict_to_cmd_packet(body: Dict[str, Any]) -> bytes:
+    save = bool(body.get("save"))
+    kw: Dict[str, Any] = {}
+    if "presets" in body:
+        kw["presets"] = body["presets"]
+    if "select" in body:
+        kw["select"] = body["select"]
+    if "default" in body:
+        kw["default"] = body["default"]
+        kw["default_targets"] = body.get("targets")
+    if "b" in body:
+        kw["brightness_0_255"] = int(body["b"])
+    return pack_cmd(pack_binary_envelope_v2(**kw), save=save)
+
+
+def build_preset_cmd_chunks(
+    presets_by_name: Dict[str, Any],
+    *,
+    save: bool = False,
+    default: Optional[str] = None,
+    max_payload: int = MAX_ESPNOW_PAYLOAD,
+) -> List[bytes]:
+    """Chunk presets into CMD packets each ≤ max_payload bytes."""
+    entries = list(presets_by_name.items())
+    chunks: List[bytes] = []
+    batch: Dict[str, Any] = {}
+
+    def _packet_for(presets_map: Dict[str, Any], *, final_save: bool, def_id: Optional[str]):
+        kw: Dict[str, Any] = {"presets": presets_map}
+        if def_id is not None:
+            kw["default"] = def_id
+        return pack_cmd(pack_binary_envelope_v2(**kw), save=final_save)
+
+    for name, preset_obj in entries:
+        trial = dict(batch)
+        trial[name] = preset_obj
+        try:
+            pkt = _packet_for(trial, final_save=False, def_id=None)
+        except ValueError:
+            pkt = b"\xff\xff"
+        if len(pkt) <= max_payload or not batch:
+            batch = trial
+        else:
+            chunks.append(_packet_for(batch, final_save=False, def_id=None))
+            batch = {name: preset_obj}
+
+    if batch:
+        chunks.append(
+            _packet_for(batch, final_save=save, def_id=str(default) if default else None),
+        )
+
+    return [c for c in chunks if c and c[0] == 0x4C]