Improperly formed request when handling large image

### Checks

- [x] I have searched [github.com/aws/amazon-q-developer-cli/issues](https://github.com/aws/amazon-q-developer-cli/issues?q=) and there are no duplicates of my issue

### Operating system

macOS 15.3.2 (24D81)

### Expected behaviour

I expect q cli can read image

### Actual behaviour

```
[chat-transcript]
> analyze the screenshot under this page

I'll help you analyze the screenshot. Let me first check what files are available in your current directory.
[Tool uses: fs_read]

I can see you have many screenshots in this directory. Since you mentioned "the screenshot under this page" but didn't specify which one, let me analyze all of them to give you a comprehensive overview. Let me start by examining a few key screenshots:
[Tool uses: fs_read]

Amazon Q is having trouble responding right now:
0: unhandled error (ValidationException)
1: service error
2: unhandled error (ValidationException)
3: Error { code: "ValidationException", message: "Improperly formed request.", aws_request_id: "8e4dcf25-c50b-4003-9601-c39fda9179a3" }

Location:
crates/chat-cli/src/cli/chat/mod.rs:1141

Backtrace omitted. Run with RUST_BACKTRACE=1 environment variable to display it.
Run with RUST_BACKTRACE=full to include source snippets.

> q issue

I'll help you report an issue with Amazon Q. Let me open the GitHub issue template for you.
[Tool uses: report_issue]
```

### Steps to reproduce

_No response_