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

lk-installers/install-ohmyposh

@@ -1 +0,0 @@
-curl -s https://ohmyposh.dev/install.sh | bash -s

lk-installers/install-ohmyposh.ps1

@@ -1,27 +0,0 @@
-#!/usr/bin/env pwsh
-<#
-.SYNOPSIS
-    Install oh-my-posh on Windows (parity with ./lk-installers/install-ohmyposh).
-.DESCRIPTION
-    Uses winget when available; otherwise falls back to the official installer.
-    No administrator rights are required (installs to the current user).
-#>
-[CmdletBinding()]
-param()
-$ErrorActionPreference = 'Stop'
-
-if (Get-Command oh-my-posh -ErrorAction SilentlyContinue) {
-    Write-Host "oh-my-posh already installed: $((Get-Command oh-my-posh).Source)"
-    return
-}
-
-if (Get-Command winget -ErrorAction SilentlyContinue) {
-    Write-Host "Installing oh-my-posh via winget..."
-    winget install JanDeDobbeleer.OhMyPosh -s winget --accept-source-agreements --accept-package-agreements
-} else {
-    Write-Host "winget not found; using the official installer script..."
-    Set-ExecutionPolicy Bypass -Scope Process -Force
-    Invoke-Expression ((New-Object System.Net.WebClient).DownloadString('https://ohmyposh.dev/install.ps1'))
-}
-
-Write-Host "Done. Open a new shell so PATH refreshes, then run .\link-dotfiles.ps1"

lk-installers/install-thefk

@@ -1,8 +0,0 @@
-#!/bin/bash
-sudo apt update
-sudo apt install python3-dev python3-pip python3-setuptools python3-venv
-python3 -m venv ~/homebase
-source ~/homebase/bin/activate
-pip3 install thefuck
-mv ~/homebase/bin/fuck ~/.local/bin/
-mv ~/homebase/bin/thefuck ~/.local/bin/