feat(gallery): make the N20 split-flap an honest Solari mechanism

The card's flip was a 0.3s drop-fade that teleported each cell straight to its target character — a suggestion of a split-flap, not one. Since the gallery card is the spec the ports get measured against, the fake would have propagated.

Three behaviors replace it, studied from the HotFX split-flap component and re-derived (its repo carries no license, so no code was copied). The charset is the drum: opts.chars declares the flap order and a changed cell steps one flap at a time through intermediates, never jumping, so cells arrive staggered by travel distance. A set() mid-cascade re-aims the running cells at the new target. The fold is real: two half-panel animations per flip — the current top falls, the next bottom lands — over four clipped layers with backfaces hidden, replacing the drop-fade keyframe.

animate:false (the reduced-motion gate) collapses every move to an instant jump. The handle grows setText, chars, and reading() so probes can sample the displayed state mid-cascade; the default width goes 3 to 4 cells, which stops truncating every demo word. Probe checks were written red first: cascade arrival, intermediate readings, one-flap-at-a-time stepping in charset order, mid-cascade retarget, and the instant animate:false path.

1 files changed, 3 insertions, 0 deletions

diff --git a/todo.org b/todo.org
index f548e03..8a52341 100644
--- a/todo.org
+++ b/todo.org
@@ -81,6 +81,9 @@ Scrolling the date module used to cycle its text format (=date-cycle= over full/
 :LAST_REVIEWED: 2026-07-13
 :END:
 Usability + documentation pass over the [[file:docs/prototypes/panel-widget-gallery.html][panel widget gallery]], orthogonal to the component-generation spec work, so it runs on the =gallery-upgrades= branch (squash merge to main after Craig's UI confirmation + tweaks). Items 1-4 run as a no-approvals speedrun (Craig authorized 2026-07-12); item 5 is a joint brainstorm after the merge.
+*** 2026-07-18 Sat @ 04:32:20 -0500 Made the N20 split-flap an honest Solari mechanism
+=GW.splitFlap= rebuilt from the drop-fade fake: charset-as-drum stepping (=opts.chars= is the flap order, one flip at a time through intermediates, staggered arrival), re-aim-not-queue retargeting, and the real two-half-panel fold (WAAPI, backfaces hidden), with =animate:false= collapsing to instant jump for reduced motion. Handle grew =setText=/=chars=/=reading()=; default width 3 → 4 cells. Nine probe checks written red-first (arrival, intermediates, one-flap stepping, re-aim discriminator, instant path); technique studied from HotFX and re-derived — no license on their repo, nothing copied (reference filed in =working/retro-stereo-widgets/references/=). Review: sound; its two test-strength notes addressed in the same change.
+
 *** 2026-07-12 Sun @ 12:59:48 -0500 Added the card size toggle (1x/2x/3x, default 3x)
 Masthead size chips apply CSS zoom per grid; 2x/3x drop the 1320px wrap cap so wide monitors get the room. CDP-verified: 84 cards, no exceptions, fader drag and toggle click both track at 3x (drag helpers are rect-ratio based, so zoom is transparent to them).
 *** 2026-07-12 Sun @ 13:42:29 -0500 Retuned the scale split per Craig