Devices: fixes from review round 7

- Removing every headset leaves none in use (commands fail at once) instead of
  falling back to the `frame` alias.
- ssh goes to the IP that answered for IPv6 too, with a link-local address's
  interface (verified: frame.local over fe80::…%en9 on the real Frame).
- Find results only show in the panel of the headset they were for.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

ui/frame_devices.py

@@ -486,6 +486,10 @@ class Registry:
         with self.lock:
             return self.data.get("active")
 
+    def emptied(self):
+        with self.lock:
+            return bool(self.data.get("emptied")) and not self.data["devices"]
+
     def set_active(self, device_id):
         with self.lock:
             self._find(device_id)
@@ -510,6 +514,7 @@ class Registry:
                 if host and not any(a["host"] == host for a in d["addresses"]):
                     d["addresses"].append(new_address(host))
             self.data["devices"].append(d)
+            self.data.pop("emptied", None)
             if not self.data.get("active"):
                 self.data["active"] = device_id
             self.save()
@@ -534,6 +539,8 @@ class Registry:
             d = self._find(device_id)
             self.data["devices"].remove(d)
             self.data.setdefault("dismissed", {})[d["alias"]] = d.get("config_host") or ""
+            if not self.data["devices"]:
+                self.data["emptied"] = True  # removed on purpose: don't fall back to the `frame` alias
             if self.data.get("active") == device_id:
                 self.data["active"] = self.data["devices"][0]["id"] if self.data["devices"] else None
             self.save()