[ZSH] Faster startup: instant prompt, single compinit, cached probes

Re-enable p10k instant prompt (sudo-key ssh-add moved above it). Drop
oh-my-zsh.sh (second compinit, update check); set up what OMZ plugins
need ourselves. Cache java_home, go env, fzf --zsh output. Disable the
kubecontext segment (ran kubectl per shell). Log starts over 1 s to
~/.cache/zsh/startup-slow.log to catch cold-start stalls.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

zsh/lib/antidote.zsh

@@ -4,9 +4,27 @@ if [[ ! -e ${ZDOTDIR:-$HOME}/.antidote ]]; then
     git clone https://github.com/mattmc3/antidote.git "${ZDOTDIR:-$HOME}/.antidote"
 fi
 
+# OMZ lib/plugins without oh-my-zsh.sh, which would set these up
+ZSH_CACHE_DIR=${ZDOTDIR:-$HOME}/.cache/zsh/omz
+[[ -d $ZSH_CACHE_DIR/completions ]] || mkdir -p "$ZSH_CACHE_DIR/completions"
+fpath=("$ZSH_CACHE_DIR/completions" $fpath)
+# ssh-agent plugin keys its env file on this; HOST changes with VPN rDNS
+SHORT_HOST=${HOST/.*/}
+if [[ $OSTYPE == darwin* ]] && _zsh_cached short_host \
+    /Library/Preferences/SystemConfiguration/preferences.plist -- scutil --get LocalHostName; then
+    read -r SHORT_HOST < $REPLY
+fi
+# OMZ calls compdef before compinit (last plugin) has run: queue, replay below
+typeset -ga _compdef_queue
+compdef() { _compdef_queue+=("${(j: :)${(@q)@}}") }
+
 zstyle ':completion:*:ssh:*' hosts off
 zstyle ':completion:*:scp:*' hosts off
 zstyle ':completion:*:commands' rehash 1
 
 source "${ZDOTDIR:-$HOME}/.antidote/antidote.zsh"
 antidote load "$plugins_txt" "$static_file"
+if (( ${+_comps} )); then
+    for _c in $_compdef_queue; do eval "compdef $_c"; done
+    unset _c _compdef_queue
+fi