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/App.css

@@ -88,7 +88,7 @@ details summary { color: var(--muted); font-size: 12px; cursor: pointer; }
 .messages { flex: 1; overflow-y: auto; padding: 8px 0; display: flex; flex-direction: column; }
 .message { display: flex; align-items: baseline; gap: 0; padding: 2px 16px; line-height: 1.5; }
 .message:hover { background: rgba(255,255,255,0.02); }
-.message-ts { color: var(--muted); font-size: 11px; white-space: nowrap; flex-shrink: 0; width: 52px; }
+.message-ts { color: var(--muted); font-size: 11px; white-space: nowrap; flex-shrink: 0; width: 72px; }
 .message-alias { font-weight: 600; font-size: 13px; text-align: left; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; flex-shrink: 0; width: 90px; padding-right: 10px; }
 .message.mine .message-alias { color: var(--accent); }
 .message-text { word-break: break-word; font-size: 14px; color: var(--text); }