transport: rename ethernet byte-layer module from socket to io

Normalizes the ethernet transport onto the canonical byte-layer name
(io.rs), including the per-OS files io_linux.rs/io_macos.rs and their
#[path] wiring. Pure file rename plus module-path and doc-comment
updates; no logic, wire, config, metric, or log change.

src/transport/ethernet/io.rs

@@ -1,7 +1,7 @@
 //! Raw Ethernet socket abstraction.
 //!
-//! Platform-specific implementations live in `socket_linux.rs` (AF_PACKET)
-//! and `socket_macos.rs` (BPF). This module re-exports `PacketSocket` and
+//! Platform-specific implementations live in `io_linux.rs` (AF_PACKET)
+//! and `io_macos.rs` (BPF). This module re-exports `PacketSocket` and
 //! provides `AsyncPacketSocket`.
 
 use crate::transport::TransportError;
@@ -11,11 +11,11 @@ pub const ETHERNET_BROADCAST: [u8; 6] = [0xff; 6];
 
 // Platform-specific PacketSocket implementation.
 #[cfg(target_os = "linux")]
-#[path = "socket_linux.rs"]
+#[path = "io_linux.rs"]
 mod platform;
 
 #[cfg(target_os = "macos")]
-#[path = "socket_macos.rs"]
+#[path = "io_macos.rs"]
 mod platform;
 
 #[cfg(unix)]

src/transport/ethernet/io_macos.rs

@@ -555,8 +555,8 @@ fn get_mac_addr(interface: &str) -> Result<[u8; 6], TransportError> {
 // ============================================================================
 // Unit tests
 //
-// The whole `socket_macos.rs` file is `#[cfg(target_os = "macos")]`-included
-// by `socket.rs`, so this `#[cfg(test)]` mod naturally only compiles on macOS.
+// The whole `io_macos.rs` file is `#[cfg(target_os = "macos")]`-included
+// by `io.rs`, so this `#[cfg(test)]` mod naturally only compiles on macOS.
 // The redundant `#[cfg(target_os = "macos")]` below is belt-and-suspenders:
 // it makes the macOS-only intent explicit so that any future refactor that
 // includes this file on additional targets won't silently activate macOS-

src/transport/ethernet/mod.rs

@@ -6,7 +6,7 @@
 //! 802.11 transparently on Linux).
 
 pub mod discovery;
-pub mod socket;
+pub mod io;
 pub mod stats;
 
 use super::{
@@ -15,7 +15,7 @@ use super::{
 };
 use crate::config::EthernetConfig;
 use discovery::{DiscoveryBuffer, FRAME_TYPE_BEACON, FRAME_TYPE_DATA, build_beacon, parse_beacon};
-use socket::{AsyncPacketSocket, ETHERNET_BROADCAST, PacketSocket};
+use io::{AsyncPacketSocket, ETHERNET_BROADCAST, PacketSocket};
 use stats::EthernetStats;
 
 use secp256k1::XOnlyPublicKey;