Keep both instructions and prompts when using subrecipes

[katzdave]

Fixes https://github.com/block/goose/issues/6078

The parameter passing was working fine, but we were only keeping instructions and not prompt which just told it it was a weather specialist and didn't have the actual parameter injection about the location it should look up.

recipe had:

instructions: |
  You are a weather data specialist. Gather current weather information
  including temperature, conditions, and seasonal context.
prompt: |
  Get the current weather for {{ location }}.