fix(companion): prompt to enable GPS when starting a trail with GPS off

Starting trail recording with GPS switched off used to call setActive(true)
immediately -- the session timer ran while the screen sat on "Waiting for
GPS fix" forever and recorded nothing, with no hint that GPS was the
problem. Choosing "Start tracking" now opens a "GPS is off" confirmation
(Enable GPS & start / Cancel); confirming enables GPS and starts the
session. Behaviour is unchanged when GPS is already on.

Gated on a new UITask::hasGPS() so the prompt only appears on boards that
expose a toggleable GPS, not where GPS is simply absent.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/solo_features/tools_screen/tools_screen.md

@@ -104,7 +104,7 @@ Cycle views with **LEFT / RIGHT**:
 
 | Item                  | Action                                              |
 | --------------------- | --------------------------------------------------- |
-| Start / Stop tracking | Begin or end a recording session                    |
+| Start / Stop tracking | Begin or end a recording session. If **GPS is off**, choosing Start asks **"GPS is off — Enable GPS & start"** so a session can't silently run with nothing to record |
 | Mark here             | Drop a waypoint at the current GPS fix (see below)  |
 | Waypoints…            | Open the waypoint list / navigation / add-by-coords |
 | Share my pos          | Send your current position as a one-shot `[LOC]` message — pick a contact or channel (see **Live Share**) |