The `html/template` package automatically HTML-escapes interpolated strings in templates. This behavior is undesirable because it causes prompts like `<h1>hello` to be escaped to `<h1>hello` before being passed to the LLM.
The included test case passes, but before the code change, it failed:
```
--- FAIL: TestModelPrompt
images_test.go:21: got "a<h1>b", want "a<h1>b"
```
