Add web-automation skill variants and inline prerequisite checks

skills/create-plan/codex/SKILL.md

@@ -7,6 +7,19 @@ description: Use when starting a new feature, project, or complex task that need
 
 Create and maintain a local plan folder under `docs/plans/` (or `docs/plan/` if that repository convention is already in use).
 
+## Prerequisite Check (MANDATORY)
+
+This skill depends on Superpowers planning skills. Before proceeding, verify required dependencies exist.
+
+Required:
+- Superpowers repo: `https://github.com/obra/superpowers`
+- `brainstorming` skill
+- `writing-plans` skill
+
+If any dependency is missing, stop immediately and return:
+
+"Missing dependency: Superpowers planning skills are required (`brainstorming`, `writing-plans`). Install from https://github.com/obra/superpowers, then retry."
+
 ## Process
 
 ### Phase 1: Bootstrap