Update assistant dynamic variables from webhook tool responses

Webhook tools can now write values directly into an assistant's dynamic variables. This lets you route tool output into prompts, actions, and insights without extra middleware or post-processing.

What's new

• Dynamic variable assignment: Map response fields to variables using response paths.
• Response path mapping: Extract values like current.precipitation from JSON responses.
• Instruction injection: Use updated variables in assistant instructions at runtime.
• Insight integration: Reference dynamic variables inside insight templates.
• Tool-driven inputs: Populate downstream fields such as transfer targets or routing logic.

Why it matters

• Reduces glue code by removing the need for external data handling.
• Improves control over model behavior using real-time tool outputs.
• Simplifies workflows by passing data across steps without reformatting.