chore(shell): powerlevel10k prompt, host-aware bootstrap, drop thefuck

- zsh prompt: replace oh-my-posh with powerlevel10k via zinit, with the
  instant-prompt preamble near the top of .zshrc for fast startup
- remove thefuck/thefk entirely: .zshrc aliases, install-thefk,
  home_config/thefuck, and its .stow-global-ignore entry
- link-dotfiles: one-shot host-aware bootstrap — detect macOS vs Linux,
  install GNU stow if missing (brew / apt/dnf/pacman), then stow both trees
- retire oh-my-posh: delete the bash + pwsh installers and
  home_config/ohmyposh (starship covers PowerShell separately)
- README: document the new bootstrap and prompt setup

home_root/.stow-global-ignore

@@ -1,5 +1,4 @@
 ~/.config/tmux/plugins
-~/.config/thefuck/__pycache__
 ~/.config/btop
 ~/.config/neofetch
 ~/.config/zinit