chore: senior-review cleanup pass

- Remove Gemini's committed update_*.py regex-surgery scripts
- Drop unused iroh-tickets dependency (hand-rolled ticket is used instead)
- Replace ToString antipattern with Display impl on PeerSpeakTicket
- Route debug log to XDG state/cache dir instead of hardcoded /home path
- Clear all compiler + clippy warnings (unused imports, collapsible ifs,
  redundant pattern matching, missing Default)

Builds clean with zero warnings.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/network/gossip.rs

@@ -114,12 +114,11 @@ impl RoomState for IrohGossipState {
                 })
             };
 
-            if let Some(payload) = initial_payload {
-                if let Ok(bytes) = serde_json::to_vec(&payload) {
+            if let Some(payload) = initial_payload
+                && let Ok(bytes) = serde_json::to_vec(&payload) {
                     crate::log_msg(&format!("Broadcasting initial state from self_id={:?}", self_id));
                     let _ = gossip_sender_clone.broadcast(bytes.into()).await;
                 }
-            }
 
             // Stream topic messages
             while let Some(res) = gossip_receiver.next().await {
@@ -186,12 +185,11 @@ impl RoomState for IrohGossipState {
                                 msg: GossipMessage::Announce(state.clone()),
                             })
                         };
-                        if let Some(payload) = payload_opt {
-                            if let Ok(bytes) = serde_json::to_vec(&payload) {
+                        if let Some(payload) = payload_opt
+                            && let Ok(bytes) = serde_json::to_vec(&payload) {
                                 crate::log_msg(&format!("Broadcasting state to new neighbor={:?}", peer_id));
                                 let _ = gossip_sender_clone.broadcast(bytes.into()).await;
                             }
-                        }
                     }
                     Ok(iroh_gossip::api::Event::NeighborDown(peer_id)) => {
                         crate::log_msg(&format!("Gossip event: NeighborDown={:?}", peer_id));