test/docs(apply): §6 M1 group-create journey + design note

`tests/group_create.rs`: a nested `[group]` tree with no server groups yet →
`pic apply --dir` creates both (parent from directory nesting), claims them for
the `[project]`, and re-applies as a no-op; a member with only editor (no
group-admin) is refused and leaves nothing behind. Design doc §6 records M1
shipped (parent-by-nesting, Phase-0 create-in-tx, claim, RBAC + attach ceiling)
with reparent/divergence still deferred to M2.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/picloud-cli/tests/cli.rs

@@ -26,6 +26,7 @@ mod email_queue;
 mod enabled;
 mod env_overlay;
 mod extension_points;
+mod group_create;
 mod group_modules;
 mod group_routes;
 mod group_scripts;