refactor: reorganize keymaps into semantic namespaces

Restructure keybindings for improved discoverability and consistency
with WezTerm/XMonad configurations. Separate keymaps from plugin
configurations following single responsibility principle.

Changes:
- Create keymaps/ directory with semantic grouping:
  - general.nix: leader setup, page navigation
  - buffers.nix: buffer operations (bq, bQ, bl)
  - windows.nix: window operations (ws, wv, wq, wQ, wm)
  - find.nix: telescope find operations (ff, fg, fh, fc)
  - git.nix: unified git operations from gitsigns/fugitive/telescope

- Adopt consistent q/Q pattern across containers:
  - bq/bQ for buffer quit (current/all others)
  - wq/wQ for window quit (current/all others)
  - Mirrors WezTerm's LEADER+p q / LEADER+t q pattern

- Extract keymaps from plugin files:
  - telescope.nix: config only, keymaps moved to find.nix
  - fugitive.nix: config only, keymaps moved to git.nix
  - gitsigns.nix: config only, keymaps moved to git.nix
  - snacks.nix: config only, keymaps moved to buffers.nix
  - maximize.nix: config only, keymap moved to windows.nix

- Remove smart-splits.nix (functionality replaced by native window ops)

- Maintain navigation on dedicated modifiers (Ctrl+arrows/PageUp/PageDown)
  for consistency with WezTerm (ALT) and XMonad (Super)

config/plugins/editor/maximize.nix

@@ -0,0 +1,13 @@
+{pkgs, ...}: {
+  extraPlugins = [
+    (pkgs.vimUtils.buildVimPlugin {
+      name = "maximize.nvim";
+      src = pkgs.fetchFromGitHub {
+        owner = "declancm";
+        repo = "maximize.nvim";
+        rev = "d688b66344b03ee6e5a32a0a40af85d174490af8";
+        hash = "sha256-rwnvX+Sul+bwESZtpqbvaDJuk49SV9tLUnvgiAH4VMs=";
+      };
+    })
+  ];
+}