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/components/Transfers.tsx

@@ -7,12 +7,13 @@ function fmt(bytes: number): string {
 }
 
 export function Transfers() {
-  const { pendingOffers, fileProgress, acceptOffer, rejectOffer, cancelTransfer, connectedPeers } = useWaste()
+  const { pendingOffers, fileProgress, resumableFiles, acceptOffer, rejectOffer, cancelTransfer, connectedPeers } = useWaste()
 
   const hasPending = Object.keys(pendingOffers).length > 0
   const hasActive = Object.keys(fileProgress).length > 0
+  const hasResumable = Object.keys(resumableFiles).length > 0
 
-  if (!hasPending && !hasActive) return null
+  if (!hasPending && !hasActive && !hasResumable) return null
 
   function alias(peerId: string) {
     return connectedPeers.find(p => p.id === peerId)?.alias ?? peerId.slice(0, 8)
@@ -22,6 +23,24 @@ export function Transfers() {
     <div className="sidebar-section">
       <span className="sidebar-label">Transfers</span>
 
+      {hasResumable && (
+        <>
+          <span className="sidebar-label" style={{ fontSize: 10, opacity: 0.6 }}>resumable</span>
+          {Object.entries(resumableFiles).map(([sha256, f]) => {
+            const pct = f.size > 0 ? Math.round((f.offset / f.size) * 100) : 0
+            return (
+              <div key={sha256} className="transfer-row">
+                <span className="transfer-name" title={f.name}>{f.name}</span>
+                <span className="transfer-meta">{fmt(f.offset)} / {fmt(f.size)} · {alias(f.from)} · will resume on reconnect</span>
+                <div className="transfer-progress">
+                  <div className="transfer-progress-bar" style={{ width: `${pct}%`, opacity: 0.5 }} />
+                </div>
+              </div>
+            )
+          })}
+        </>
+      )}
+
       {Object.entries(pendingOffers).map(([xid, offer]) => (
         <div key={xid} className="transfer-row">
           <span className="transfer-name" title={offer.name}>{offer.name}</span>