feat: add self-disable step to template setup workflow

[jpke]

This PR adds a clever self-modifying feature to the template setup workflow that optimizes context window usage.

Problem

The template setup workflow needed to be visible during initialization () so agents could see the detailed instructions, but this caused the detailed instructions to consume context window space even after the one-time setup was complete.

Solution

Added a final step to the template setup workflow that instructs the agent to change to after template initialization is complete.

How it Works

1. During template initialization: The rule is visible () so agents can see detailed instructions
2. After template setup is complete: The agent changes the frontmatter to
3. Future sessions: The detailed template setup instructions don't consume context window space
4. If needed later: Instructions can still be accessed via the reference in workflow.mdc

Benefits

• ✅ Detailed instructions available during one-time setup
• ✅ Context window space preserved after setup is complete
• ✅ Self-managing rule that optimizes itself automatically
• ✅ No loss of functionality - instructions remain accessible when needed

Changes Made

• Added "Final Step: Remove from Context Window" section to template_setup.mdc
• Provides clear instructions for the agent to modify the rule's frontmatter
• Explains the purpose and benefits of this optimization

This creates an elegant solution for managing context usage while maintaining accessibility to detailed instructions.