fix: compact timestamps, historical alias resolution, wider ts column

- Timestamps now show "Jun 28 10:58" for older messages (dropped
  "Yesterday" which overflowed the fixed-width column)
- Timestamp column widened from 52px to 72px to fit date+time
- state_snapshot now includes known_peers (historically seen, not
  currently connected) so the UI can resolve aliases in history
- MessagePane aliasFor falls back to knownPeers map

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/src/types.ts

@@ -117,6 +117,7 @@ export interface IpcMessage {
   master_id?: string
   local_peer?: PeerInfo
   connected_peers?: PeerInfo[]
+  known_peers?: PeerInfo[]
   rooms?: string[]
   networks?: NetworkInfo[]
   error_message?: string