Q CLI enters corrupted state after use_aws with s3 ls command - all subsequent responses fail with ValidationException

### 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 15.6.1 (24G90)

### Expected behaviour

After use_aws command completes successfully, Q CLI should process the response normally and continue functioning for subsequent messages

### Actual behaviour

Using tool: use_aws
⋮
● Running aws cli command:

Service name: s3
Operation name: ls
Parameters:
- : "s3://****REDACTED****/"
Profile name: ****REDACTED****
Region: us-east-1

Allow this action? Use 't' to trust (always allow) this tool for the session. [y/n/t]:

[****REDACTED****] > y

Label: Listar archivos en root de ****REDACTED****con s3 ls
⋮
● Completed in 0.861s

Amazon Q is having trouble responding right now:
0: Failed to send the request: unhandled error (ValidationException)
1: unhandled error (ValidationException)
2: service error
3: unhandled error (ValidationException)
4: Error { code: "ValidationException", message: "Improperly formed request.", aws_request_id: "a0858b26-5fbb-4a91-b0b7-9db4cbd8d7d8" }

Location:
crates/chat-cli/src/cli/chat/mod.rs:1073

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

### Steps to reproduce

1. Execute use_aws tool with service_name: "s3" and operation_name: "ls"
2. Command executes successfully ("Completed in 0.861s")
3. Q CLI fails to process the response and shows ValidationException
4. Any subsequent user message (even simple "hello") triggers the same ValidationException
5. Q CLI becomes completely unusable until restart

### Environment

```yaml

[q-details]
version = "1.16.2"
hash = "c4c80bb44cb22b6e19129ed7475f2793ff20135d"
date = "2025-09-19T01:27:56.356289Z (4d ago)"

[system-info]
os = "macOS 15.6.1 (24G90)"
chip = "Apple M3 Pro"
total-cores = 12
memory = "18.00 GB"

[environment]
cwd = "/Users/USER/Downloads"
cli-path = "/Users/USER/Downloads"
install-method = "unknown"

[env-vars]
PATH = "/opt/homebrew/Caskroom/miniconda/base/bin:/opt/homebrew/Caskroom/miniconda/base/condabin:/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"
QTERM_SESSION_ID = "becd2caedbee4f6fb9a720fb1ec4c47d"
Q_SET_PARENT_CHECK = "1"
Q_TERM = "1.16.2"
SHELL = "/bin/zsh"
TERM = "xterm-256color"
__CFBundleIdentifier = "com.googlecode.iterm2"

[chat-settings]

[chat-trusted_tools]
@datetime=trusted
fs_write=trusted
@aws-mcp-cache=trusted
fs_read=trusted
@simple-task-manager=trusted

[chat-failed_request_ids]
none

[chat-context]
current_profile=backspc
profile_context=
/Users/****REDACTED****/.aws/q/global-context.md

files=
/Users/****REDACTED****/.aws/q/global-context.md, 1960 tkns
total context size=1960 tkns
```