🎨 Palette: [UX] Add loading spinners for model validation

[sl4m3]

💡 What: Added rich.console.status loading spinners with "dots" to model validation steps in the init command (OpenRouter API, CLI tools, AI Studio API).
🎯 Why: API calls and CLI subprocesses can take several seconds to complete, making the setup interface feel frozen or unresponsive. Spinners reassure users the process is actively working.
📸 Before/After: Before, a static text message would sit until the request finished. After, the text has an animated dots spinner.
♿ Accessibility: Improves cognitive accessibility by providing immediate and continuous visual feedback on system status.

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PR created automatically by Jules for task 9212727442052824566 started by @sl4m3

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