feat: resumable transfer UX — surface partial downloads to UI on reconnect

Daemon scans the download directory for .tmp.meta sidecars on network join
and emits resumable_transfers IPC event. Web UI shows them in the Transfers
panel with a dimmed progress bar and "will resume on reconnect" note.

- proto: ResumableFile type, EvtResumableTransfers, resumable_files IpcMessage field
- mesh: ScanResumable() scans download dir and emits the event
- netmgr: call ScanResumable() after join (both Join and JoinByHash paths)
- web: resumableFiles store state, resumable_transfers handler, Transfers UI section

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

web/src/store/index.ts

@@ -55,6 +55,8 @@ interface WasteState {
   pendingOffers: Record<string, { peerId: string; name: string; size: number }>
   // active in-progress transfers: xid → progress
   fileProgress: Record<string, { peerId: string; name: string; received: number; total: number }>
+  // partial downloads found on daemon startup: sha256 → info
+  resumableFiles: Record<string, { name: string; from: string; size: number; offset: number }>
 
   // actions
   connect: (url: string) => void
@@ -96,6 +98,7 @@ export const useWaste = create<WasteState>((set, get) => ({
   sharedFilesByNetwork: {},
   pendingOffers: {},
   fileProgress: {},
+  resumableFiles: {},
 
   connect(url: string) {
     const adapter = new DaemonAdapter(url)
@@ -355,6 +358,14 @@ export const useWaste = create<WasteState>((set, get) => ({
         }
         break
       }
+      case 'resumable_transfers': {
+        const files = (msg.resumable_files ?? []) as Array<{ name: string; sha256: string; from: string; size: number; offset: number }>
+        if (files.length === 0) break
+        const byHash: Record<string, { name: string; from: string; size: number; offset: number }> = {}
+        for (const f of files) byHash[f.sha256] = { name: f.name, from: f.from, size: f.size, offset: f.offset }
+        set(s => ({ resumableFiles: { ...s.resumableFiles, ...byHash } }))
+        break
+      }
       case 'history_loaded': {
         const room = msg.room
         const incoming = (msg.messages ?? []) as ChatMessage[]