🎨 Palette: [Chat UI] Add disabled states when neuro-link is offline

[teerthsharma]

💡 What: Added dynamic disabled states to the chat input and send button, tied to the kernel's tunnelStatus.
🎯 Why: Previously, users could attempt to type and send messages even when the neuro-link tunnel was offline, leading to silent failures and a confusing user experience. Now, the input is visibly disabled and explains why.
📸 Before/After: Visual changes verified via Playwright. When offline, the input displays "Neuro-Link Offline..." and the button is disabled.
♿ Accessibility: Updated aria-label and title attributes dynamically to provide screen-reader context for why the elements are disabled ("System offline"). Added disabled:opacity-50 and disabled:cursor-not-allowed styles.

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PR created automatically by Jules for task 911136967904974849 started by @teerthsharma

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