Session 48: Wire format design and logging improvements

Wire format:
- Add HandshakeMessageType enum (NoiseIKMsg1=0x01, NoiseIKMsg2=0x02)
- Define unified TLV framing for handshake and post-handshake messages
- Update fips-design.md and fips-protocol-flow.md with wire format details

Initialization:
- Defer TUN setup until after peer connections initiated
- Order: packet channel → transports → peers → TUN

Logging cleanup:
- Consolidate node/TUN info logs into aligned multi-line format
- TUN shutdown: single start/stop message, remove intermediate noise
- Remove ip link show callout and redundant Starting node message
- Change UDP transport stopped to debug level

src/node.rs

@@ -244,12 +244,6 @@ impl Node {
             .sign_declaration(&identity)
             .expect("signing own declaration should never fail");
 
-        info!(
-            node_id = %node_id,
-            address = %identity.address(),
-            "Node initialized as root"
-        );
-
         Ok(Self {
             identity,
             config,
@@ -293,12 +287,6 @@ impl Node {
             .sign_declaration(&identity)
             .expect("signing own declaration should never fail");
 
-        info!(
-            node_id = %node_id,
-            address = %identity.address(),
-            "Node initialized as root"
-        );
-
         Self {
             identity,
             config,
@@ -1032,12 +1020,10 @@ impl Node {
         }
 
         self.state = NodeState::Running;
-        info!(
-            state = %self.state,
-            transports = self.transports.len(),
-            connections = self.connections.len(),
-            "Node started"
-        );
+        info!("Node started:");
+        info!("       state: {}", self.state);
+        info!("  transports: {}", self.transports.len());
+        info!(" connections: {}", self.connections.len());
         Ok(())
     }