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/luasnip.lua

@@ -1,18 +1,2 @@
-return {
-  "L3MON4D3/LuaSnip",
-  enabled = true,
-  version = "v2.*",
-  build = "make install_jsregexp",
-  event = "InsertEnter",
-  dependencies = {
-    "rafamadriz/friendly-snippets",
-  },
-  config = function(plugin, opts)
-    -- run the default astronvim config that calls the setup call
-    require "astronvim.plugins.configs.luasnip"(plugin, opts)
-    -- lazy load snippets from friendly-snippets
-    require("luasnip.loaders.from_vscode").lazy_load()
-    -- add more custom luasnip configuration such as filetype extend or custom snippets
-    require("luasnip").filetype_extend("javascript", { "javascriptreact" })
-  end,
-}
+-- LuaSnip is configured in completion.lua
+return {}