feat(nvim): phase 3 — replace nvim-cmp with blink.cmp and telescope with snacks.picker

Swap the completion engine to blink.cmp v1.x, dropping nvim-cmp,
its eight cmp-* sources, lspkind, and LuaSnip. Swap the picker
to snacks.picker, removing telescope.nvim and six telescope
extensions. LSP capabilities now sourced from blink.cmp; LSP
navigation keymaps and the colorscheme/keymaps/todo pickers move
to Snacks.picker. friendly-snippets is preserved as blink's
snippet source.

lua/absolute/after/todo-comments.lua

@@ -14,9 +14,9 @@ vim.keymap.set("n", "]t", function()
     todo_comments.jump_next()
 end, opts)
 
-opts.desc = "Open Comments in Telescope"
+opts.desc = "Open todo comments in picker"
 vim.keymap.set("n", "<leader>pt", function()
-    vim.cmd([[TodoTelescope]])
+    Snacks.picker.todo_comments()
 end, opts)
 
 opts.desc = "Open Comments in Trouble"