fix(version-exchange): also store peer commit on the listen side

Previously the Hello handler in `ListenTask` echoed our local commit
back but deliberately threw away the peer's, on the assumption that
the outgoing connect-side path (`connect.rs:278-279` →
`set_peer_commit`) would always populate the visible state for any
bidirectionally-configured peer.

That assumption breaks any time the *outgoing* TCP/DTLS direction is
broken even though the inbound direction is fine — happened just now
when the peer Mac's daemon stopped listening on 4242 (DHCP-renewed
IP, daemon crashed, asymmetric NAT, …). Mac was still happily
connecting in the other direction and sending events, including the
initial Hello, but Linux silently displayed "peer version unknown"
because the listen side dropped Mac's commit on the floor.

Add a `PeerHello { addr, commit }` EmulationEvent variant fired from
the listen-side Hello handler. The service maps `addr → ClientHandle`
via `client_manager.get_client(addr)` and calls `set_peer_commit` +
`broadcast_client` exactly like the connect path does. The connect
path remains the primary source for symmetric setups; this is the
defensive fallback so version visibility doesn't depend on outbound
reachability.

Skips silently when no outgoing client is configured for the peer's
addr (incoming-only setup) — there's no UI row to update in that
case anyway.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/service.rs

@@ -319,6 +319,17 @@ impl Service {
             EmulationEvent::Connected { addr, fingerprint } => {
                 self.notify_frontend(FrontendEvent::DeviceConnected { addr, fingerprint });
             }
+            EmulationEvent::PeerHello { addr, commit } => {
+                // Map the peer's source addr back to its client handle
+                // and stamp the commit. Skip if we don't have an
+                // outgoing client configured for this peer (incoming-
+                // only setup) — there's nowhere to display the version
+                // in that case anyway.
+                if let Some(handle) = self.client_manager.get_client(addr) {
+                    self.client_manager.set_peer_commit(handle, Some(commit));
+                    self.broadcast_client(handle);
+                }
+            }
         }
     }