feat: render history_loaded in web UI with earlier messages divider

- store: handle history_loaded event — prepend gossipped messages,
  dedup by mid, sort by ts, record cutoff timestamp per room
- MessagePane: show "earlier messages" divider between history and
  live messages based on the cutoff timestamp
- types: add history_loaded, room_created, create_room to IpcMsgType;
  add messages field to IpcMessage

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

web/src/App.css

@@ -158,3 +158,5 @@ details summary { color: var(--muted); font-size: 12px; cursor: pointer; }
 .file-entry-dir { cursor: pointer; }
 .file-entry-dir:hover { background: rgba(255,255,255,0.04); }
 .file-entry-icon { font-size: 12px; flex-shrink: 0; }
+.history-divider { display: flex; align-items: center; gap: 8px; margin: 10px 0 6px; color: var(--muted); font-size: 11px; }
+.history-divider::before, .history-divider::after { content: ''; flex: 1; height: 1px; background: var(--border); }

web/src/components/MessagePane.tsx

@@ -2,10 +2,11 @@ import { useEffect, useRef, useState } from 'react'
 import { useWaste } from '../store'
 
 export function MessagePane() {
-  const { messages, activeRoom, activeNetworkId, localPeer, connectedPeers, send } = useWaste()
+  const { messages, historyCutoff, activeRoom, activeNetworkId, localPeer, connectedPeers, send } = useWaste()
   const [draft, setDraft] = useState('')
   const bottomRef = useRef<HTMLDivElement>(null)
   const roomMessages = messages[activeRoom] ?? []
+  const cutoff = historyCutoff[activeRoom] ?? 0
 
   useEffect(() => {
     bottomRef.current?.scrollIntoView({ behavior: 'smooth' })
@@ -46,11 +47,19 @@ export function MessagePane() {
           const mine = msg.from === localPeer?.id
           const alias = aliasFor(msg.from)
           const time = new Date(msg.ts).toLocaleTimeString([], { hour: '2-digit', minute: '2-digit', hour12: false })
+          const showDivider = cutoff > 0 && i > 0 && roomMessages[i - 1].ts <= cutoff && msg.ts > cutoff
           return (
-            <div key={msg.mid ?? i} className={`message ${mine ? 'mine' : ''}`}>
-              <span className="message-ts">{time}</span>
-              <span className="message-alias">{alias}</span>
-              <span className="message-text">{msg.text}</span>
+            <div key={msg.mid ?? i}>
+              {showDivider && (
+                <div className="history-divider">
+                  <span>earlier messages</span>
+                </div>
+              )}
+              <div className={`message ${mine ? 'mine' : ''}`}>
+                <span className="message-ts">{time}</span>
+                <span className="message-alias">{alias}</span>
+                <span className="message-text">{msg.text}</span>
+              </div>
             </div>
           )
         })}

web/src/store/index.ts

@@ -32,6 +32,8 @@ interface WasteState {
 
   // chat — keyed by room
   messages: Record<string, ChatMessage[]>
+  // rooms for which we have received history: room → ts of last history message
+  historyCutoff: Record<string, number>
   activeRoom: string
   // user-created rooms, keyed by networkId
   customRooms: Record<string, string[]>
@@ -84,6 +86,7 @@ export const useWaste = create<WasteState>((set, get) => ({
   activeNetworkId: null,
   connectedPeers: [],
   messages: {},
+  historyCutoff: {},
   activeRoom: 'general',
   customRooms: {},
   fileLists: {},
@@ -352,6 +355,24 @@ export const useWaste = create<WasteState>((set, get) => ({
         }
         break
       }
+      case 'history_loaded': {
+        const room = msg.room
+        const incoming = (msg.messages ?? []) as ChatMessage[]
+        if (!room || incoming.length === 0) break
+        set(s => {
+          const existing = s.messages[room] ?? []
+          const existingMids = new Set(existing.map(m => m.mid).filter(Boolean))
+          const fresh = incoming.filter(m => !m.mid || !existingMids.has(m.mid))
+          if (fresh.length === 0) return s
+          const merged = [...fresh, ...existing].sort((a, b) => a.ts - b.ts)
+          const cutoff = fresh[fresh.length - 1]?.ts ?? 0
+          return {
+            messages: { ...s.messages, [room]: merged },
+            historyCutoff: { ...s.historyCutoff, [room]: cutoff },
+          }
+        })
+        break
+      }
     }
   },
 }))

web/src/types.ts

@@ -82,6 +82,9 @@ export type IpcMsgType =
   | 'shares_list'
   | 'peer_status'
   | 'error'
+  | 'history_loaded'
+  | 'room_created'
+  | 'create_room'
 
 export interface IpcMessage {
   type: IpcMsgType
@@ -124,4 +127,6 @@ export interface IpcMessage {
   conn_state?: PeerConnState
   candidate_type?: CandidateType
   remote_address?: string
+  // history_loaded
+  messages?: ChatMessage[]
 }