fix: prevent plan mode layering with planning skills

Bot consistently enters EnterPlanMode before invoking writing-plans,
creating redundant approval gates and read-only restrictions. Add
red flag entry to using-superpowers and explicit warning to
writing-plans skill.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

skills/using-superpowers/SKILL.md

@@ -81,6 +81,7 @@ These thoughts mean STOP—you're rationalizing:
 | "I'll just do this one thing first" | Check BEFORE doing anything. |
 | "This feels productive" | Undisciplined action wastes time. Skills prevent this. |
 | "I know what that means" | Knowing the concept ≠ using the skill. Invoke it. |
+| "Let me enter plan mode first" | If a skill handles planning (writing-plans, brainstorming), use the skill directly. EnterPlanMode is redundant — never layer it with a planning skill. |
 
 ## Skill Priority
 

skills/writing-plans/SKILL.md

@@ -5,6 +5,8 @@ description: Use when you have a spec or requirements for a multi-step task, bef
 
 # Writing Plans
 
+**IMPORTANT:** Invoke this skill directly — do NOT use EnterPlanMode or platform plan mode. This skill has its own workflow and approval checkpoint (execution handoff). Layering plan mode on top is redundant and restrictive.
+
 ## Overview
 
 Write comprehensive implementation plans assuming the engineer has zero context for our codebase and questionable taste. Document everything they need to know: which files to touch for each task, code, testing, docs they might need to check, how to test it. Give them the whole plan as bite-sized tasks. DRY. YAGNI. TDD. Frequent commits.