Feature Request: User-Friendly Error Handling for Input Page

### **Overview**

Currently, when an error occurs on the input page (e.g., unsupported file type), the error message is displayed **inside the input text area**, which is confusing and not user-friendly.

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### **Steps to Reproduce**

1. Navigate to the input page where the user submits files or text.
2. Add a file with an unsupported type or submit invalid input.
3. Observe that the error is injected into the input area, which breaks the input’s purpose and confuses users.

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### **Expected Behavior**

* The input area should **remain untouched** (no error text inside).
* A **popup modal**, **toast notification**, or **alert banner** should appear clearly explaining the issue.
* The user should be able to dismiss the error easily.
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