/plan-feature

Add a new feature to an existing project by generating new phases and integrating them into IMPLEMENTATION_PHASES.md and SESSION.md.

# Plan Feature

Add a new feature to an existing project by generating new phases and integrating them into IMPLEMENTATION_PHASES.md and SESSION.md.

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## Your Task

Follow these steps to plan and integrate a new feature into an existing project.

### 1. Check Prerequisites

Check that planning docs exist:


**If SESSION.md doesn't exist:**
- Output: "❌ No SESSION.md found. This command is for existing projects."
- Suggest: "For new projects, use /plan-project instead."
- Stop

**If IMPLEMENTATION_PHASES.md doesn't exist:**
- Output: "❌ No IMPLEMENTATION_PHASES.md found."
- Suggest: "Cre...