viewer: a scheme hovered in the menu is shown live

Owner, 2026-10-19: hovering a scheme for a moment switches to it live;
moving off goes to the next one hovered or back to the one in force, to
sample schemes without re-opening the menu.

A variant's row rested on for 50 ms is worn; off every row for 50 ms,
the scheme in force again; the menu closed without a click, the one in
force at once. Only a click chooses, and a preview is never kept.
Tested with frames 10 ms apart.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj

docs/color-schemes.md

@@ -7,7 +7,11 @@ and the viewer's own two). The menu's filter narrows the list to light or
 dark schemes. Families are listed alphabetically, each one's variants too,
 in as many columns as the window's height needs, so every family is on
 screen at once; a variant's whole row (its colors and its name) chooses
-it.
+it. Resting the pointer on a variant's row for 50 ms wears it live, to
+sample schemes without choosing; off the rows, the next one hovered or the
+scheme in force is worn again, and closing the menu without a click puts
+back the one in force. Only a click chooses, and only a chosen scheme is
+kept.
 The choice is a viewer preference, kept with eframe's other preferences;
 nothing is written to the books, and no figure or word changes with the
 scheme (`schemes.rs`, `painted`).

docs/testing.md

@@ -452,7 +452,11 @@ menu, its scroll bar hidden), the families not alphabetical, and a click on
 a variant's colors doing nothing. Now the families are alphabetical, in
 columns with no scrolling, and a variant's whole row is its button;
 `every_family_is_on_screen_in_order_and_a_whole_row_chooses` checks all
-three in a tall window and a short one. Earlier: the viewer's own light palette's green below 4.5:1 on the
+three in a tall window and a short one. The live preview (owner, the same
+day) is checked by `a_hovered_scheme_is_shown_live_and_only_a_click_keeps_it`
+with frames 10 ms apart: not worn before 50 ms, worn after, the next row's
+scheme on moving, the one in force off the rows and at once on closing,
+nothing kept until a click. Earlier: the viewer's own light palette's green below 4.5:1 on the
 sidebar (4.35:1), and a first fix (moving colors toward the text color)
 that turned Everforest's red and green into the same grey; colors keep
 their hue and change only lightness.