🎨 Palette: Add visual feedback for model validation

[sl4m3]

💡 What: Replaced static print statements with dynamic rich.console.status spinners during model validation API calls and subprocess executions in the CLI. Added rich.markup.escape to safely display dynamic model names.
🎯 Why: Long-running blocking operations like network requests or subprocesses without visual feedback make the application appear frozen, leading to a poor user experience.
📸 Before/After: N/A (CLI visual enhancement)
♿ Accessibility: Provides immediate visual confirmation that a background task is actively running and has not stalled.

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PR created automatically by Jules for task 1279813493093820960 started by @sl4m3

[google-labs-jules]

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