Update README

Goals

• Keep every README in the repo accurate for the current codebase.
• Ensure README explains the nix directory layout for common packages/settings and host-specific configuration placement.
• Remove outdated or no-longer-true statements.
• Write in concise English.

Workflow

1. Discover README targets

• List README files with rg --files -g 'README*' from the repo root.
• Only the top-level README.md is permitted; subdirectory READMEs are not allowed.
• If any subdirectory README files exist, remove them and consolidate their content into the top-level README.

2. Determine scope for the README

• The top-level README.md must be the only README in the repo.
• Use the filesystem to confirm what exists before writing.

3. Rewrite the README

• Keep content minimal; include ## Setup and ## Nix layout.
• ## Setup
  • Describe the exact setup steps required now.
  • Include copy-pasteable commands in Markdown code blocks so the setup can be executed directly.
  • Remove deprecated steps or tooling references.
• ## Nix layout
  • Explain where common packages/settings live and where host-specific configuration lives inside nix/.
  • Use short sentences or bullets; avoid excessive detail.

4. Remove obsolete content

• Delete any badges, deprecated sections, or instructions that are no longer true.
• If a section cannot be substantiated from current files, remove it.

Output expectations

• English only.
• No extra sections beyond the required two.
• For the root README, never mention deprecated folders (like init/) or non-active folders unless instructed.
• Only README.md at repo root may exist; delete any others.

Notes

• This repo treats git/, nvim/, wezterm/, and zsh/ as the active configuration roots.
• If a README claims to manage files or scripts that no longer exist, remove those claims.