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/presence.lua

@@ -1,4 +1,2 @@
-return {
-  "andweeb/presence.nvim",
-  event = "VimEnter",
-}
+-- Removed: not part of the from-scratch config
+return {}