Make the offered home address the one that gets used, and keep edits safe

An interrupted review pass pointed at four problems in the pill's dialog, each
confirmed against the Frame:

- The offer to add the Frame's LAN address appended it after the Tailscale name,
  which then kept winning on that network, so nothing changed. The offer now adds
  it first in the list (address-add takes first: true); away from home the
  Tailscale name still leads. A tested address that ranks above the one in use
  gets a Use now button that reconnects through it.
- A half-typed edit was thrown away when the connection state changed after
  focus left the input, and when the server refused the save. The edit row now
  stays until it is saved or cancelled.
- Pressing Enter twice sent the update twice.
- The offer's button could act on the previously selected headset.

Keyboard focus also stays on the same button of the same address when the rows
are rebuilt.

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

docs/devices.md

@@ -76,8 +76,11 @@ services and checks `ALIAS.local` and `frame.local`.
 **The pill's dialog** lists the same addresses, with what each one answered, and
 can add, edit, reorder and remove them without leaving the page you're on. When
 the headset reports a LAN IP on the same network as this computer and that IP
-isn't saved, it offers to add it, so at home the app connects directly rather
-than over Tailscale. A new or edited address is tested straight away.
+isn't saved, it offers to add it. The offer puts the address first in the list,
+so on that network it wins over the Tailscale name; away from home the Tailscale
+name still leads. A new or edited address is tested straight away. When a tested
+address ranks above the one in use, **Use now** reconnects through it; otherwise
+the change takes effect the next time Frame Control connects.
 
 ## Networks