feat(installers): consolidate app installers into host-aware install-apps

Fold macinstaller + install-apt-pkgs + install-tools + install-zellij into a
single host-aware lk-installers/install-apps (macOS->Homebrew, bootstrapping
Homebrew if absent; Linux->apt + upstream installers). Installs the tools the
configs assume (bat, fd, fzf, zoxide, zellij, nvim, btop, htop, tldr) plus the
fzf-git.sh helper and fzf shell integration; idempotent.

link-dotfiles gains --apps to install then link in one shot. .zshrc drops the
redundant brew/system zsh-autosuggestions source (zinit already loads it),
fixing the missing-file error on a fresh box. README documents the new flow.

link-dotfiles

@@ -15,6 +15,14 @@ set -euo pipefail
 repo="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 cd "$repo"
 
+# `--apps`: install all host CLI tools first, then link. Without it, this only
+# links (fast + idempotent). App install is delegated to the host-aware
+# lk-installers/install-apps.
+if [ "${1:-}" = "--apps" ]; then
+  echo "Installing apps first (--apps)…"
+  "$repo/lk-installers/install-apps"
+fi
+
 ensure_stow() {
   command -v stow >/dev/null 2>&1 && return
 
@@ -22,7 +30,7 @@ ensure_stow() {
   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
+        echo "error: Homebrew is required on macOS. Run ./lk-installers/install-apps (or ./link-dotfiles --apps) first." >&2
         exit 1
       fi
       brew install stow