Playground bugs: stale errors and error-container overlap

## Bug Report: React-PDF Playground Usability Issues

The React PDF Playground exhibits several usability problems that hinder code editing and testing.

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### **1. Stale Error Messages**
- **What happens:**
After fixing an error in the code editor, the error message remains visible and does not clear until the entire page is refreshed.
- **Expected behavior:**
Error messages should disappear immediately once the underlying code is corrected.

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### **2. Error Container Overlap**
- **What happens:**
When an error is displayed, its container overlaps the bottom of the code editor, preventing visibility and editing of the affected lines.
- **Expected behavior:**
The error panel should be docked, resizable, or otherwise non-overlapping so the full code remains accessible.

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### **Suggestions**
🔸 Automatically clear error messages when code compiles successfully
🔸 Dock or resize the error panel to avoid covering code

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### **Steps to Reproduce**
1. Navigate to the [React-PDF Playground](https://react-pdf.org/repl)
2. Introduce a typo (e.g., `` instead of ``)
3. Observe the error message appear

4. Fix the typo back to ``
5. Notice the error message **remains**

6. Paste or write a long block of code and scroll to the bottom
7. Observe the error panel overlapping the code


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### **Environment**
- **Browser:** Brave v1.78.102
- **OS:** Windows 11

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Thank you for maintaining this project—these fixes would greatly improve the developer experience in the playground!