error while generating diagram

### 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
- [x] I have run `q doctor` in the affected terminal session
- [x] I have run `q restart` and replicated the issue again

### Operating system

macOS 15.4.1 (24E263)

### Expected behaviour

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: "a8f3b3bd-796b-41b9-a710-97dfa414c2dc" }

Location:
/private/tmp/788abf33-519d-4264-918b-e563eeb425ff/crates/q_chat/src/lib.rs:1015

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

### Actual behaviour

failed

### Steps to reproduce

_No response_

### Environment

```yaml

[q-details]
version = "1.9.1"
hash = "REMOVED"
date = "2025-04-29T06:22:42.917989Z (12d ago)"
variant = "full"

[system-info]
os = "macOS 15.4.1 (24E263)"
chip = "Apple M3"
total-cores = 8
memory = "16.00 GB"

[environment]
cwd = "/Users/USER"
cli-path = "/Users/USER"
os = "Mac"
shell-path = "/bin/zsh"
shell-version = "5.9"
terminal = "macOS"
install-method = "unknown"

[env-vars]
PATH = "/opt/homebrew/bin:/Library/Frameworks/Python.framework/Versions/3.12/bin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/Users/USER/.local/bin"
QTERM_SESSION_ID = "e9b7f37bc6194e799e7ab92dedfb5268"
Q_SET_PARENT_CHECK = "1"
Q_TERM = "1.9.1"
SHELL = "/bin/zsh"
TERM = "xterm-256color"
__CFBundleIdentifier = "com.apple.Terminal"
```