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/editing.lua

@@ -0,0 +1,68 @@
+return {
+  -- Auto-close brackets, with LaTeX math guard
+  {
+    "windwp/nvim-autopairs",
+    event = "InsertEnter",
+    config = function()
+      local npairs = require("nvim-autopairs")
+      local Rule = require("nvim-autopairs.rule")
+      local cond = require("nvim-autopairs.conds")
+
+      npairs.setup({
+        check_ts = true,
+        ts_config = { java = false }, -- disable for Java (interferes with jdtls)
+        fast_wrap = { map = "<M-e>" },
+      })
+
+      -- LaTeX inline math: $...$ pair
+      npairs.add_rules({
+        Rule("$", "$", { "tex", "latex" })
+          :with_pair(cond.not_after_regex("%%"))   -- don't pair after %
+          :with_move(cond.none())
+          :with_del(cond.not_after_regex("xx"))
+          :with_cr(cond.none()),
+      })
+    end,
+  },
+
+  -- Surround operations: ys, cs, ds
+  {
+    "kylechui/nvim-surround",
+    version = "*",
+    event = "VeryLazy",
+    opts = {},
+  },
+
+  -- Formatter (format on save)
+  {
+    "stevearc/conform.nvim",
+    event = "BufWritePre",
+    cmd = "ConformInfo",
+    keys = {
+      { "<leader>lf", function() require("conform").format({ async = true, lsp_fallback = true }) end, desc = "Format" },
+    },
+    opts = {
+      formatters_by_ft = {
+        lua             = { "stylua" },
+        rust            = { "rustfmt" },
+        javascript      = { "prettier" },
+        typescript      = { "prettier" },
+        javascriptreact = { "prettier" },
+        typescriptreact = { "prettier" },
+        svelte          = { "prettier" },
+        java            = { "google-java-format" },
+        json            = { "prettier" },
+        yaml            = { "prettier" },
+        toml            = { "taplo" },
+        html            = { "prettier" },
+        css             = { "prettier" },
+        markdown        = { "prettier" },
+        ["jinja.html"]  = { "djlint" },
+      },
+      format_on_save = {
+        timeout_ms = 2000,
+        lsp_fallback = true,
+      },
+    },
+  },
+}