nvim,tmux,kitty: full config overhaul (AstroNvim → native 0.12)

Replaces AstroNvim v5 with from-scratch Neovim 0.12 config using
vim.lsp.config()/vim.lsp.enable() natively, lazy.nvim, blink.cmp,
and smart-splits tmux integration.

tmux: new C-Space prefix, hjkl pane nav, resize key table, tpm plugins.
kitty: add allow_remote_control for smart-splits.

dot_config/nvim/lua/plugins/nabla.lua

@@ -1,19 +1,2 @@
--- Lightweight inline ASCII preview for LaTeX math
-return {
-  "jbyuki/nabla.nvim",
-  ft = { "tex", "plaintex", "markdown" },
-  keys = {
-    -- Popup preview for the expression under cursor
-    { "<leader>mp", function() require("nabla").popup() end, desc = "Math: popup preview" },
-
-    -- Toggle inline virtual rendering; re-enable wrap after toggle (nabla toggles it off)
-    {
-      "<leader>mv",
-      function()
-        require("nabla").toggle_virt { autogen = true }
-        vim.wo.wrap = true
-      end,
-      desc = "Math: toggle inline preview",
-    },
-  },
-}
+-- Removed: not part of the from-scratch config
+return {}