Live Share was the only "leave it on and forget" broadcast mode with no
at-a-glance cue, unlike auto-advert/trail/repeater which all blink in the top
bar. Reuses the diamond already used for a live-tracked contact on the map,
so the glyph already means "sharing position" elsewhere in the UI. Also
fixes the Tools-list "Live Share" row to use ICON_GPS instead of ICON_ADVERT
(which collided with the Auto-Advert row) — currently inert since per-row
icons are disabled there, but correct for whenever they're re-enabled.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>