style: normalize whitespace and line endings in shell scripts

- Standardize indentation and spacing across install.sh and lib files
- Fix line ending inconsistencies for better cross-platform compatibility
- Improve curl flag usage in neovim.sh (-kLo with explicit temp path)
- Add theme persistence functionality to remember user's colorscheme choice

These changes improve code consistency and add the ability to save/restore
the selected theme across sessions.

lib/neovim.sh

@@ -13,11 +13,11 @@ if command -v nvim &>/dev/null; then
 fi
 
 if $NVIM_NEEDED; then
-  curl -kLO https://github.com/neovim/neovim/releases/latest/download/nvim-linux-x86_64.tar.gz
+  curl -kLo /tmp/nvim-linux-x86_64.tar.gz https://github.com/neovim/neovim/releases/latest/download/nvim-linux-x86_64.tar.gz
   sudo rm -rf /opt/nvim-linux-x86_64
-  sudo tar -xzf nvim-linux-x86_64.tar.gz -C /opt
+  sudo tar -xzf /tmp/nvim-linux-x86_64.tar.gz -C /opt
   sudo ln -sf /opt/nvim-linux-x86_64/bin/nvim /usr/local/bin/nvim
-  rm nvim-linux-x86_64.tar.gz
+  rm -f /tmp/nvim-linux-x86_64.tar.gz
   info "Neovim installed: $(nvim --version | head -1)"
 fi
 
@@ -100,6 +100,18 @@ LUA
 # ── LSP (clangd) ───────────────────────────────────────────────
 mkdir -p "$NVIM_CFG/lua/configs"
 
+cat >"$NVIM_CFG/lua/plugins/lspconfig.lua" <<'LUA'
+return {
+  {
+    "neovim/nvim-lspconfig",
+    config = function()
+      require("nvchad.configs.lspconfig").defaults()
+      require "configs.lspconfig"
+    end,
+  },
+}
+LUA
+
 cat >"$NVIM_CFG/lua/configs/lspconfig.lua" <<'LUA'
 local configs = require "nvchad.configs.lspconfig"