🎨 Palette: Improve empty state message for checkpoints

[ivangegovdve-sudo]

💡 What: Updated the checkpoint list empty state message to include the actionable command for creating a checkpoint.
🎯 Why: A generic "No checkpoints found" message leaves users at a dead-end. Providing the command right there (checkpoint create <name>) makes the CLI significantly more intuitive and user-friendly.
📸 Before/After:
Before:
No checkpoints found.

After:
No checkpoints found. Use 'checkpoint create <name>' to create one.
♿ Accessibility: N/A, text-based CLI improvement.

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PR created automatically by Jules for task 1934569057972367073 started by @ivangegovdve-sudo

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[gemini-code-assist]

Code Review

This pull request updates the CLI to provide actionable instructions when no checkpoints are found, aligning with a new design principle added to the project's documentation. Specifically, it modifies the checkpoint list command to suggest the checkpoint create command when the list is empty. I have no feedback to provide.