feat(keymaps): add normal-mode NES keymap and enable native inline completion

Adds a normal-mode <Tab> binding that calls sidekick.nes_jump_or_apply() so
NES suggestions can be accepted without entering insert mode. Enables
vim.lsp.inline_completion so the insert-mode <Tab> chain (snippet → NES →
native inline completion → fallback) is fully wired. Updates the README
keymaps table to reflect both modes and the complete Tab chain.

lua/plugins.lua

@@ -395,6 +395,9 @@ lazyload.on_vim_enter(function()
 		},
 	})
 
+	-- Enable native inline completion (ghost text in insert mode)
+	vim.lsp.inline_completion.enable()
+
 	-- Mini.ai
 	vim.pack.add({ { src = "https://github.com/echasnovski/mini.ai", name = "mini.ai" } })