feat(accessibility): home-side Hyprland companion

New nomarchy.accessibility.enable home option mirroring
nomarchy.system.accessibility.enable. When enabled, core/home/
accessibility.nix contributes a Hyprland extraConfig block via
lib.mkAfter:

  - input.repeat_rate = 25 (from 40)
  - input.repeat_delay = 1000 ms (from 600)
    Holding a key isn't a runaway machine-gun for low-mobility users.

  - bindd = SUPER ALT, S, Launch Orca, exec, orca
    The system preset already puts orca on PATH.

mkAfter guarantees the slowdown wins over the templated input.conf.
Documented in docs/OPTIONS.md. The third item from the original Next
row — a high-contrast palette — is split into its own Later row
because it's a design task (24-colour WCAG AAA palette + icon family
choice) that wants its own review.

`nix flake check --no-build` clean.

core/home/default.nix

@@ -10,5 +10,6 @@
     ./security.nix
     ./bash.nix
     ./gaming.nix
+    ./accessibility.nix
   ];
 }