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/mason.lua

@@ -1,28 +1,2 @@
-if true then return {} end -- WARN: REMOVE THIS LINE TO ACTIVATE THIS FILE
-
--- Customize Mason
-
----@type LazySpec
-return {
-  -- use mason-tool-installer for automatically installing Mason packages
-  {
-    "WhoIsSethDaniel/mason-tool-installer.nvim",
-    -- overrides `require("mason-tool-installer").setup(...)`
-    opts = {
-      -- Make sure to use the names found in `:Mason`
-      ensure_installed = {
-        -- install language servers
-        "lua-language-server",
-
-        -- install formatters
-        "stylua",
-
-        -- install debuggers
-        "debugpy",
-
-        -- install any other package
-        "tree-sitter-cli",
-      },
-    },
-  },
-}
+-- Mason is configured in lsp.lua
+return {}