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, 1 insertions, 1 deletions

diff --git a/docs/prototypes/panel-widget-gallery.html b/docs/prototypes/panel-widget-gallery.html
index a31f578..201fa0e 100644
--- a/docs/prototypes/panel-widget-gallery.html
+++ b/docs/prototypes/panel-widget-gallery.html
@@ -948,7 +948,7 @@ const INFO={
   origin:'Nixie tubes.',difficulty:'Intuitive.',
   prefer:'Warmth and era matter more than crispness.',
   period:'1955-75 hard period: sits with keypads and telegraphs, clashes with VFD and LED seven-seg.'},
-'N20':{input:'Display only; flaps animate on change.',
+'N20':{input:'Click steps to the next word. Each cell flips one flap at a time through its charset, so cells arrive staggered; a mid-spin change re-aims the cascade.',
   solves:'A changed value that announces itself mechanically.',
   use:'Specialty. Shines for arrivals-board style updates.',
   limits:'Character set and flap speed are the charm and the constraint.',