Motion flavours, and Lift is shadow, rim or auto: auto on a dark page recedes the other panes (InactiveDim)

Motion off|crisp|smooth|bouncy|playful is one parameter set (animation.Motion)
every fx animation reads. One focus spring per pane drives both the lift and
the dim, at the flavour's pace; a grid snaps.

Lift drops glow and surface. A shadow falls on pane bodies and rails only,
capped so text and the selection keep min(contrast, 4.5); rim is a hairline
along the focused tag's top. auto is a shadow on a light page; on a dark page
the core recedes the unfocused panes' text (InactiveDim, ported from 2e4d97f,
default 30 under auto) with the same floor. Tests: focused text contrast is
never below unfocused in any style, dim or theme; the focused pane's cells and
tag are untouched by a dim.

Shared files: src/config.zig, src/builtins.zig, src/ninep/ctl.zig,
src/surface.zig, src/detached/wire.zig, docs/config.md,
test/snapshots/builtins.snap (one more wheel for the longer help).

1 files changed, 15 insertions, 0 deletions

diff --git a/docs/config.md b/docs/config.md
index 16fd59e5..83fbd0eb 100644
--- a/docs/config.md
+++ b/docs/config.md
@@ -527,6 +527,21 @@ the chain empty the pass is bypassed. CRT works in linear light with restrained
 scanlines, mask, bloom and vignette, and no curvature, so clicks land where
 they are drawn.
 
+The focused pane can stand off the page (SDL GUI, off by default):
+
+```text
+Lift shadow      a soft drop shadow, on the other panes' bodies only
+Lift rim         a hairline just above the focused tag (light, or shade on a light page)
+Lift auto        a shadow on a light page; on a dark one the others recede
+Lift off
+InactiveDim 30   the unfocused panes' text fades 30% toward its ground
+Motion smooth    off, crisp, smooth, bouncy or playful
+```
+
+`InactiveDim` works everywhere (a grid shows it at once) and never takes a
+pair below its own contrast or 4.5. Under `Lift auto` on a dark page it is 30
+while unset. `Motion` sets how every such effect moves: see docs/effects.md.
+
 `EffectCode PanelAscii` or `EffectCode Crt` lists the current backend's
 build-embedded source paths under `/virtual`. Look opens each full file;
 no checkout is needed, but the build must carry them (`-Dembed-sources=true`,