Agent Skills: research-add-fields

Append new field definitions to an in-progress research outline's `fields.yaml` — either from user-supplied input or from a web-search agent that proposes common dimensions in the domain. Use mid-`/research-outline` when you've realised the schema is missing dimensions (e.g. pricing, performance, ecosystem, governance) before running `/research-deep`, so deep agents fill the new fields on first pass instead of needing a re-run.