pi: caveman mode

♠ Previously, previously. Problem statement: adopt caveman in pi. Pi isn’t one of the 30+ agents caveman auto-detects. The install matrix (INSTALL.md) lists agent detection rules one by one — claude, cursor, windsurf, opencode, openclaw, etc — and pi isn’t in it. Running the one-liner installer here would just skip everything silently. Booo! Rather than run someone else’s curl | bash against an agent it wasn’t built for, “““I””” reimplemented the terse-speak part natively, since pi already ships the two primitives needed: skills and extensions. A skill for /skill:caveman documentation, and an extension that rewrites the system prompt on every turn via pi.on("before_agent_start", (event) => ...): const INSTRUCTIONS = `Caveman mode: on. Respond terse. Drop articles (a/an/the), filler (just/really/basically), pleasantries, hedging. Fragments OK. Short synonyms. Technical terms exact. Pattern: [thing] [action] [reason]. [next step]. Example — not: "Sure! I'd be happy to help you with…