Add rustfmt formatting policy and reformat codebase

Add rustfmt.toml with stable defaults and apply cargo fmt to all
source files. This establishes a consistent formatting baseline
for CI enforcement.

src/node/session.rs

@@ -7,10 +7,10 @@
 
 use std::time::Instant;
 
+use crate::NodeAddr;
 use crate::config::SessionMmpConfig;
 use crate::mmp::MmpSessionState;
 use crate::noise::{HandshakeState, NoiseSession};
-use crate::NodeAddr;
 use secp256k1::PublicKey;
 
 /// State machine for an end-to-end session.
@@ -159,12 +159,16 @@ impl SessionEntry {
     /// Get the current session state.
     #[cfg(test)]
     pub(crate) fn state(&self) -> &EndToEndState {
-        self.state.as_ref().expect("session state taken but not restored")
+        self.state
+            .as_ref()
+            .expect("session state taken but not restored")
     }
 
     /// Get mutable access to the session state.
     pub(crate) fn state_mut(&mut self) -> &mut EndToEndState {
-        self.state.as_mut().expect("session state taken but not restored")
+        self.state
+            .as_mut()
+            .expect("session state taken but not restored")
     }
 
     /// Replace the session state.
@@ -278,7 +282,12 @@ impl SessionEntry {
 
     /// Get traffic counters: (packets_sent, packets_recv, bytes_sent, bytes_recv).
     pub(crate) fn traffic_counters(&self) -> (u64, u64, u64, u64) {
-        (self.packets_sent, self.packets_recv, self.bytes_sent, self.bytes_recv)
+        (
+            self.packets_sent,
+            self.packets_recv,
+            self.bytes_sent,
+            self.bytes_recv,
+        )
     }
 
     // === Handshake Resend ===