2026-02-06: Port from Prompty to Jinja2 for prompt templating

We were previously using Prompty for prompt templating. We have moved from Prompty to Jinja2 since we are preparing to move from Chat Completions to Responses (which Prompty does not support), plus Prompty did not achieve wide community adoption. Jinja2 is a widely supported templating framework, and Prompty was based off Jinja2, so the prompt templates look similar. However, we are only using Jinja2 to template individual messages, not the entire conversation like before.

What's Changed

• Fix multimodal image download from non-default blob container by @pamelafox in #2951
• Bump certifi from 2024.7.4 to 2026.1.4 by @dependabot[bot] in #2949
• Bump pyjwt from 2.10.1 to 2.11.0 by @dependabot[bot] in #2948
• Revert Yarn GPG workaround and use built-in devcontainer image by @Copilot in #2956
• Fix ty type checker errors breaking nightly jobs by @Copilot in #2958
• Migrate from Prompty to Jinja2 for prompt templates by @pamelafox in #2953

Full Changelog: 2026-01-27...2026-02-06