feat(ui): surface transfer progress, cancel, and delivery events

Make the transfer loop feel live: parse real core progress payloads, show
progress on send/receive surfaces, allow cancel/stop, retry failed receives,
and fix delivery-phase events so receiver completion updates the UI.

crates/vnidrop/CORE_FLOW.md

@@ -36,7 +36,7 @@ bytes through Kotlin memory.
 - Transfer statuses: `sharing`, `receiving`, `done`, `failed`, `cancelled`,
   `stopped`.
 - Main event phases: `endpoint`, `import`, `ticket`, `handshake`, `approval`,
-  `access`, `transfer`, `download`, `export`, `lifecycle`, `error`.
+  `access`, `transfer`, `download`, `export`, `delivery`, `lifecycle`, `error`.
 - Events are sent to `CoreEventSink` immediately and persisted through the event
   hub. `list_events` flushes queued persistence before reading SQLite.
 - `shutdown()` is idempotent and flushes events before stopping the router.

crates/vnidrop/src/event_hub.rs

@@ -45,6 +45,8 @@ enum EventPhase {
     Handshake,
     Approval,
     Transfer,
+    /// Delivery receipts from receivers (completed download acknowledgements).
+    Delivery,
 }
 
 impl EventPhase {
@@ -65,6 +67,7 @@ impl EventPhase {
             "handshake" => Some(Self::Handshake),
             "approval" => Some(Self::Approval),
             "transfer" => Some(Self::Transfer),
+            "delivery" => Some(Self::Delivery),
             _ => None,
         }
     }
@@ -86,6 +89,7 @@ impl EventPhase {
             Self::Handshake => "handshake",
             Self::Approval => "approval",
             Self::Transfer => "transfer",
+            Self::Delivery => "delivery",
         }
     }
 }

crates/vnidrop/tests/approval.rs

@@ -55,6 +55,14 @@ fn public_share_receives_without_sender_approval() {
     assert_eq!(deliveries[0].receiver_name.as_deref(), Some("Receiver"));
     assert_eq!(deliveries[0].status, "completed");
     assert!(deliveries[0].completed_at.is_some());
+    assert!(
+        sender.sink.events().iter().any(|event| {
+            event.phase == "delivery"
+                && event.kind == "receiver-completed"
+                && event.transfer_id == Some(share.transfer_id)
+        }),
+        "delivery receipts must emit a delivery phase event for UI live updates"
+    );
 }
 
 #[test]