prompt with template that get user message as input do not supported, so long for @openspec

### 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 15.6.0 (24G84)

### Expected behaviour

@openspec-proposal "my text"

### Actual behaviour

@openspec-proposal --> get not parameters subtitution

### Steps to reproduce

install open-spec, do openspec init, try @openspec-proposal prompt

### Environment

```yaml

[q-details]
version = "1.19.2"
hash = "a27549280100ff844ee50882676d5c9ca74d309a"
date = "2025-10-28T03:24:23.387223Z (10d ago)"

```