Add pre-chat message activity HTML test and removed starterPromptCar…

[jcheung824]

ADO issue: https://msazure.visualstudio.com/CCI/_workitems/edit/32481620/

Description

• Design expectation of having no starter prompt during blueprint state.

Design

https://www.figma.com/design/r8dKrVWy43ZFAMUQir2AgD/RS-Agent-Builder?node-id=3062-48739&m=dev

Specific Changes

• Remove starter prompt card when the current ui state is blueprint state

• [x] I have added tests and executed them locally
• [x] I have updated CHANGELOG.md
• [ ] I have updated documentation

Review Checklist

This section is for contributors to review your work.

• [ ] Accessibility reviewed (tab order, content readability, alt text, color contrast)
• [ ] Browser and platform compatibilities reviewed
• [ ] CSS styles reviewed (minimal rules, no z-index)
• [ ] Documents reviewed (docs, samples, live demo)
• [ ] Internationalization reviewed (strings, unit formatting)
• [ ] package.json and package-lock.json reviewed
• [ ] Security reviewed (no data URIs, check for nonce leak)
• [ ] Tests reviewed (coverage, legitimacy)

[jcheung824]

@microsoft-github-policy-service agree company="Microsoft"