create a new job chat sub agent

[josephjclark]

• use new search tool
• drop support for old prompt
• any other breaking changes we want to make?

Does this service send code inline, or as an attachment/suggestion?

Options:

1. always send code attachments, and if the user isn't in context (Ie, not in the inspector), navigate them there.
2. Always send an attachment but let lightning decide how to render it - as a diff? As a code block?
3. Optionally send an attachment, subject to the payload