add caveman compression mode to agent bootstrap

AGENTS.md now instructs every agent to communicate
tersely. CAVEMAN.md holds the full rules. Agents
apply from first message in each session.

AGENTS.md

@@ -83,7 +83,12 @@ Grep is fine for browsing or when MCP is unreachable.
 - **Wiki updates**: same-session rule applies to any meaningful state change
   this client makes.
 
-## 6. Auto-setup mechanism
+## 6. Communication mode
+
+Read and apply `/opt/homelab-context/CAVEMAN.md` (if present). It defines the lab's
+terse-communication standard — drop filler, keep substance, use fragments.
+
+## 7. Auto-setup mechanism
 
 The homelab-context repo ships tooling that gets automatically installed
 on every client after `git pull`. This is handled by `tools/post-pull.sh`
@@ -104,7 +109,7 @@ commit and push. All enrolled clients pick it up within 5 minutes.
 
 To trigger sync manually: `sudo homelab sync` or wait for the 5-min timer.
 
-## 7. When in doubt
+## 8. When in doubt
 
 Run `homelab mcp search_docs <query>` or `homelab mcp get_host <name>`.
 The clone is the fallback; MCP is the index.