Merge branch 'refactor-transport' into refactor-next

Forward-merge the transport neighbor-beacon rename (ethernet + BLE
discovery -> neighbor module/buffer rename; ethernet config discovery
flag -> listen with serde alias). Hand-resolved the module files against
next's identity-out-of-beacon beacon rewrite by starting from next's
bodies and re-applying the rename by identifier, so next's beacon logic
(no-arg build_beacon, bool parse_beacon, computed BEACON_SIZE, one-arg
add_peer, deleted BLE add_peer_with_pubkey) is preserved unchanged.

testing/chaos/sim/config_gen.py

@@ -67,7 +67,7 @@ def _build_ethernet_config(iface: str) -> dict:
     """Build an Ethernet transport config dict for a single interface."""
     return {
         "interface": iface,
-        "discovery": True,
+        "listen": True,
         "announce": True,
         "auto_connect": True,
         "accept_connections": True,