chore: drop makima/Typora/xournalpp; gate fcitx5/voxtype/opencode behind options

Tier A removals — small, half-wired modules nobody had asked for:

- makima (Copilot-key remapper): drop core/system/makima.nix, the
  features/apps/makima/ keyboard.toml, the nomarchy-restart-makima script,
  the `nomarchy.system.features.makima` option, the state-file binding,
  the import in core/system/default.nix, and the "Key Remapping" entry
  in nomarchy-menu. ~50 LoC + a service nobody asked for.
- Typora theme dir (core/home/config/Typora/) — Typora is a paid tool
  Nomarchy doesn't even ship; the SUPER+SHIFT+W keybinding pointed at a
  binary that wasn't on PATH.
- xournalpp settings (core/home/config/xournalpp/) — referenced
  /usr/share paths that don't exist on NixOS.
- core/home/config/environment.d/fcitx.conf — manual env vars are
  redundant once fcitx5 routes through NixOS's i18n.inputMethod.

Optionalization — three half-wired features now sit behind explicit
toggles, all default off (except keyring which keeps its existing
default-on):

- nomarchy.system.inputMethod.enable: new core/system/input-method.nix
  uses NixOS's i18n.inputMethod with fcitx5 + mozc/chinese/table addons.
  Drops the Hyprland exec-once line — i18n.inputMethod handles autostart.
- nomarchy.system.voxtype.enable: marker option for users who install
  voxtype out-of-band (it's not in nixpkgs). Today it just documents
  intent; the existing keybinding + waybar widget no-op gracefully.
- nomarchy.apps.opencode.enable: gates the existing
  features/apps/opencode/default.nix xdg.configFile so the opencode
  config only deploys when the user opts in.

Installer:
- system.nix and home.nix templates now surface the new toggles in their
  "Optional Nomarchy modules" comment blocks.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

core/system/default.nix

@@ -17,12 +17,12 @@
     ./network.nix
     ./impermanence.nix
     ./browser.nix
-    ./makima.nix
     # Tier 1 system features (all opt-in via nomarchy.system.*).
     ./snapper.nix
     ./hibernate.nix
     ./containers.nix
     ./pam.nix
+    ./input-method.nix
     ../../themes/engine/plymouth.nix
     ../../themes/engine/sddm.nix
   ];