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

link-dotfiles

@@ -1,3 +1,53 @@
-#!/bin/bash
+#!/usr/bin/env bash
+# One-shot, host-aware dotfile linker for Linux & macOS.
+#
+#   home_root/*    ->  ~/<name>           (e.g. ~/.zshrc)       via `stow home_root`
+#   home_config/*  ->  ~/.config/<name>   (e.g. ~/.config/nvim) via `stow home_config`
+#
+# Ensures GNU stow is present first (Homebrew on macOS; apt/dnf/pacman on Linux),
+# so a fresh box needs nothing pre-installed. Re-running is safe — stow is
+# idempotent and refuses to clobber unrelated real files.
+#
+# Windows / PowerShell: run ./link-dotfiles.ps1 instead (stow has no native
+# Windows port; the .ps1 mirrors this with junctions + symlinks).
+set -euo pipefail
+
+repo="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+cd "$repo"
+
+ensure_stow() {
+  command -v stow >/dev/null 2>&1 && return
+
+  echo "GNU stow not found — installing it…"
+  case "$(uname -s)" in
+    Darwin)
+      if ! command -v brew >/dev/null 2>&1; then
+        echo "error: Homebrew is required on macOS. Run ./lk-installers/macinstaller first." >&2
+        exit 1
+      fi
+      brew install stow
+      ;;
+    Linux)
+      if   command -v apt    >/dev/null 2>&1; then sudo apt update && sudo apt install -y stow
+      elif command -v dnf    >/dev/null 2>&1; then sudo dnf install -y stow
+      elif command -v pacman >/dev/null 2>&1; then sudo pacman -S --noconfirm stow
+      else
+        echo "error: no supported package manager (apt/dnf/pacman). Install GNU stow manually." >&2
+        exit 1
+      fi
+      ;;
+    *)
+      echo "error: unsupported OS '$(uname -s)'. On Windows run ./link-dotfiles.ps1 instead." >&2
+      exit 1
+      ;;
+  esac
+}
+
+ensure_stow
+
+echo "Linking home_root  -> ~"
 stow -v home_root
-stow -v --target=$HOME/.config/ home_config
+echo "Linking home_config -> ~/.config"
+stow -v --target="$HOME/.config" home_config
+
+echo "Done."