Start Modify Assistant

Start an EDIT-MODE setup assistant call to modify an existing template via AI.

Always creates a fresh interview + session — never resumes a prior one. The edit-mode framing is composed at this layer:

1. The existing template's full JSON is rendered into EDIT_MODE_PREAMBLE and PREPENDED to the Setup Assistant's system_instructions (after its own {available_skills} placeholder is resolved). This puts the artifact-under-edit and the "you are not onboarding from scratch" framing at the very top of the agent's prompt.
2. The interview's goals are replaced with EDIT_MODE_GOALS — a single open-ended goal capturing what the user wants changed and why.
3. interviews.context.edit_mode_template_id = <template_id> tells the webhook (after the call completes) to run the edit-path synthesis and PATCH the existing template, instead of creating a new one.