🎨 Palette: Improve status bar error context and state resets

[raccioly]

💡 What

Updated vscode-extension/extension.js to ensure the status bar explicitly resets its background color when transitioning to an unknown state (backgroundColor = undefined). Also, updated the error catch block to clearly show an error icon, error background, and the exact error message in the tooltip, instead of silently fading to an unknown state.

🎯 Why

When execSpecguard failed or returned non-JSON content, the extension either showed an unhelpful CDD: ? with lingering background colors from previous warnings, or completely hid the error message. This micro-UX improvement ensures developers have accurate, context-aware visual feedback and don't get confused by lingering red/yellow backgrounds on unknown states.

📸 Before/After

Before: If the score fell below threshold (yellow background), and then a CLI error occurred, the status bar showed $(shield) CDD: ? but kept the yellow background. Error states were swallowed entirely.
After: Error states show $(error) CDD: Error with a red background and the error in the tooltip. Unknown states explicitly clear the background color.

♿ Accessibility

Improves cognitive accessibility by providing consistent, clear context for state changes via explicit tooltips, rather than relying solely on icons or potentially stale background colors.

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PR created automatically by Jules for task 13486129242837321735 started by @raccioly

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