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/lsp/ltex.lua

@@ -0,0 +1,38 @@
+-- LTeX grammar/spell checking for LaTeX and Markdown
+-- ltex_extra.nvim manages dictionaries/rules persistence
+vim.lsp.config("ltex", {
+  filetypes = { "tex", "plaintex", "bib", "markdown" },
+  settings = {
+    ltex = {
+      checkFrequency = "save",
+      language = "en-GB",
+      additionalRules = { motherTongue = "de-DE" },
+      dictionary = {
+        ["en-GB"] = {},
+        ["de-DE"] = {},
+        ["fr-FR"] = {},
+      },
+      disabledRules = {
+        ["en-GB"] = {},
+        ["de-DE"] = {},
+        ["fr-FR"] = {},
+      },
+      hiddenFalsePositives = {
+        ["en-GB"] = {},
+        ["de-DE"] = {},
+        ["fr-FR"] = {},
+      },
+    },
+  },
+  on_attach = function(client, bufnr)
+    local ok, ltex_extra = pcall(require, "ltex_extra")
+    if ok then
+      ltex_extra.setup({
+        load_langs = { "en-GB", "de-DE", "fr-FR" },
+        init_check = true,
+        path = ".ltex",
+        log_level = "none",
+      })
+    end
+  end,
+})