* chore(home): drop AstroNvim bundle and centralize editors
Remove the bundled Neovim plugin tree to shrink supply-chain exposure; keep a
minimal programs.neovim backup. Daily editing stays Helix-first with Yazi and
Zellij.
- Add Helix/Neovim docs, glossary, and cheatsheets under core/editors/.
- Default EDITOR/VISUAL to hx; use SUDO_EDITOR nvim --clean for sudoedit and
other sensitive edits; adjust Nushell buffer_editor accordingly.
- Apply Helix Home Manager settings (keys, editor UI) in core/editors/helix.
- Keep heavy language-server tooling only in home/base/tui/editors/packages.nix;
wire it via an explicit default.nix import so core stays lightweight.
- Extend modules/base packages.nix where that profile sets global editor env.
* docs: link editors, VS Code, and agents from README
Document tui/editors versus core/editors; add root README pointers to GUI
vscode (Home Manager) and agents/. Cross-link heavy packages README from
core/editors.
