docs(using-git-worktrees): update Integration descriptions (PRI-823)

Clarify that skill ensures a workspace exists, not that it always creates one.

skills/using-git-worktrees/SKILL.md

@@ -233,9 +233,9 @@ Ready to implement auth feature
 ## Integration
 
 **Called by:**
-- **brainstorming** (Phase 4) - REQUIRED when design is approved and implementation follows
-- **subagent-driven-development** - REQUIRED before executing any tasks
-- **executing-plans** - REQUIRED before executing any tasks
+- **brainstorming** - REQUIRED: Ensures isolated workspace (creates one or verifies existing)
+- **subagent-driven-development** - REQUIRED: Ensures isolated workspace (creates one or verifies existing)
+- **executing-plans** - REQUIRED: Ensures isolated workspace (creates one or verifies existing)
 - Any skill needing isolated workspace
 
 **Pairs with:**