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/texlab.lua

@@ -0,0 +1,20 @@
+vim.lsp.config("texlab", {
+  settings = {
+    texlab = {
+      build = {
+        executable = "latexmk",
+        args = { "-pdf", "-interaction=nonstopmode", "-synctex=1", "%f" },
+        onSave = false,
+        forwardSearchAfter = false,
+      },
+      chktex = {
+        onOpenAndSave = false,
+        onEdit = false,
+      },
+      diagnosticsDelay = 300,
+      formatterLineLength = 80,
+      bibtexFormatter = "texlab",
+      latexFormatter = "latexindent",
+    },
+  },
+})