Switch the screenshot convention from positional numbers (tls_scr_8) to
self-documenting names (locator, locator_picker, map_target, …). Names say what
they show, so a shot can be re-captured or inserted without renumbering, and a
reference can't silently point at the wrong image. Per-doc directories keep the
names unambiguous, so no prefix is needed (overview_oled.png lives in each
screen's own folder).
git mv on every existing PNG + ref updates across all six solo_features docs;
the pending placeholders adopt the same scheme.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>