Dropping the expression pick whip on one of a property's values (the X
of Position) referenced the whole property. As in After Effects, a
drop on one value now picks that dimension: `transform.position[0]`;
a drop on the name still picks the whole property.
`prop.pickWhip` takes `target.dimension`.
The rest of #363 is unchanged: inserting at the cursor landed with
#284, and After Effects' property pick whip in the Parent & Link
column is left for later.
Tests: pick_whip_picks_one_dimension_of_the_target (engine),
the_expression_pick_whip_picks_the_dimension_it_is_dropped_on
(ui_inline_edit).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
6fadae2818