feat(setup): optional bootstrap-ai.sh to install Ollama + pull a model

Keeps bootstrap.sh AI-free by default; bootstrap-ai.sh layers on the local
model runtime (transparent, opt-in install) for the /ai agent.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bootstrap.sh

@@ -77,3 +77,4 @@ echo
 echo "ready. next steps:"
 echo "    cd hh && ./lets-hack.sh          # local test session (server + clients in tmux)"
 echo "    # or run the server + client by hand — see README.MD"
+echo "    # want the local AI agent? ./bootstrap-ai.sh  (installs Ollama + a model)"