feat(pi): first-class support via pi-subagents + pi-ask-user (#651)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.md

@@ -193,6 +193,13 @@ bunx @every-env/compound-plugin install compound-engineering --to gemini
 bunx @every-env/compound-plugin install compound-engineering --to kiro
 ```
 
+**Pi prerequisites.** Pi does not ship a native subagent primitive, so the Pi install depends on [nicobailon/pi-subagents](https://github.com/nicobailon/pi-subagents) (required) and recommends [edlsh/pi-ask-user](https://github.com/edlsh/pi-ask-user) for richer blocking user questions:
+
+```bash
+pi install npm:pi-subagents    # required — provides the `subagent` tool used by skills that dispatch parallel agents
+pi install npm:pi-ask-user     # recommended — provides the `ask_user` tool; skills fall back to numbered options in chat when it is missing
+```
+
 To auto-detect custom-install targets and install to all:
 
 ```bash