G1: Lift, soft elevation shadows (off by default)

`Lift` (a GUI toggle, capability lift) lifts the focused pane on a
critically damped spring (animation.Spring: closed form, about 240 ms to
settle, velocity kept across retargets, settled = no frames) and floats
notices. The core puts the lift on the regions (Region.lift, on the wire);
the GUI casts from it: a soft shadow is decor, an erf rectangle on one
quad grown by 3 sigma (decor.frag, flag 0x10000000), in the quad's own
space so a track's transform carries it; darken-only, the caster's rect
left alone, alpha pre-warped for linear light and IGN-dithered. Cast last
in its group, so a neighbour's rails and rules darken with its text; a
notice's before its rule. Strength is capped per theme so text over the
darkest shadow keeps min(its contrast, 4.5) (test over the native themes).

Opt-in until the focus lift/dim default is decided. Feel review material:
docs/effects.md. Test-mode PARDES_TEST_SERIES keeps every captured frame.

Shared files touched: pardes.zig (two fields, one nextWake line),
detached/wire.zig (lift on the region), config.zig, builtins.zig
(capability), gui.zig. Not touched: Messages.zig, mouse.zig, tty,
host_io.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/builtins.zig b/src/builtins.zig
index 23d853c8..53cf0999 100644
--- a/src/builtins.zig
+++ b/src/builtins.zig
@@ -28,6 +28,8 @@ pub const capabilities: config.Runtime.Capabilities = .{
     // Only the SDL shell shapes with HarfBuzz and honours the setting. macOS
     // draws CoreText ligatures of its own, but nothing there reads it yet.
     .ligatures = pardes.platform == .gui,
+    // Soft shadows are the SDL shell's decor.
+    .lift = pardes.platform == .gui,
 };
 
 /// Where a builtin acts: at the pane it runs from, or on the editor as a