bug: Persistent “Improperly formed request.” error after upgrading to Amazon Q 1.13.0

### 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 15.6 (Sequoia)

### Expected behaviour

After Amazon Q finishes answering a question, the conversation should end normally without showing any error messages.

### Actual behaviour

Since updating to version 1.13.0 on 2025-07-31, Amazon Q consistently shows the same error message right after completing its answer (see below).
This issue has persisted for several days. I have already reported it to the official BD, but it remains unresolved.
I also tried removing my existing profile data and reconfiguring the Agent from scratch, but the error still occurs.

Error message example:
```
2025-08-11T05:57:17.946481Z ERROR chat_cli::telemetry: 595: Failed to send cw telemetry event err=ValidationError [ValidationException]: Improperly formed request.: service error: ValidationError [ValidationException]: Improperly formed request.
```

### Steps to reproduce

1. Use Amazon Q version 1.13.0 (updated after 2025-07-31).
2. Start an Agent session and ask any question.
3. Wait for Amazon Q to finish answering.
4. Immediately after the answer completes, the above error message appears in the terminal.

### Environment

```yaml
[q-details]
version = "1.13.2"
hash = "e44ee53d76813a5ef107dcd0d6181b089cb5b2f2"
date = "2025-08-08T20:32:47.811878Z (2d ago)"
variant = "full"

[system-info]
os = "macOS 15.6.0 (24G84)"
chip = "Apple M1 Pro"
total-cores = 8
memory = "32.00 GB"

[environment]
cwd = "/Users/USER"
cli-path = "/Users/USER"
os = "Mac"
shell-path = "/bin/zsh"
shell-version = "5.9"
terminal = "iTerm 2"
install-method = "brew"

[env-vars]
PATH = "/opt/homebrew/opt/php@8.2/sbin:/opt/homebrew/opt/php@8.2/bin:/Users/USER/.codeium/windsurf/bin:/opt/homebrew/opt/mysql-client/bin:/Users/USER/.local/bin:/Users/USER/.nvm/versions/node/v23.1.0/bin:/Users/USER/.oh-my-zsh/custom/plugins/git-open:/usr/local/opt/coreutils/libexec/gnubin:/Users/USER/bin:/Users/USER/.local/bin:/usr/local/bin:/Applications/Sublime Text.app/Contents/SharedSupport/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/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:/Applications/iTerm.app/Contents/Resources/utilities:/Users/USER/.local/bin:/opt/homebrew/opt/fzf/bin:/Users/USER/Library/Python/3.13/bin"
QTERM_SESSION_ID = "7a59af796a22487ea953bd6661578663"
Q_SET_PARENT_CHECK = "1"
Q_TERM = "1.13.2"
Q_USING_ZSH_AUTOSUGGESTIONS = "1"
SHELL = "/bin/zsh"
TERM = "xterm-256color"
__CFBundleIdentifier = "com.googlecode.iterm2"
```