Better support for terminal editors (nvim, helix): avoid stdio: 'inherit', reuse running instances #161

Clicking "open in editor" from Vite / Vue DevTools / Nuxt DevTools doesn't really work with terminal editors today:

1. TUI editors are spawned with stdio: 'inherit', so they share the dev server's terminal (often busy or in another window) instead of getting their own.
2. nvim and hx aren't recognized: no line/column args in get-args.js, and they're missing from isTerminalEditor, so each click spawns another instance.

LAUNCH_EDITOR (#39 / #49) is a good escape hatch, and I understand built-in TUI handling may be out of scope. I'd like to propose, and am happy to implement:

• Small code change: add nvim (same args as vim) and hx (file:line:col) to the arg mappings, isTerminalEditor, and the editor lists.
• A README section on terminal editors, documenting LAUNCH_EDITOR recipes in three layers:
  • open a new window of the default terminal;
  • open a tab or split in the terminal the dev server runs in (kitty / wezterm / ghostty remote control);
  • open in a tmux or zellij pane.
  • For reuse: if this project already has an nvim running, open the file as a buffer via nvim --server <socket> --remote instead of starting a new process. Helix has no remote-open API yet (Implement Kakoune-style client-server model for sharing buffers across windows in different terminals helix-editor/helix#312), so for now it relies on the multiplexer approach.

Would you accept a PR for the mappings plus docs? If you'd rather keep any of this out of the core library, docs only works for me too.