Rich text notes on Opportunities

Opportunities now support a note_html field for rich text notes, alongside the existing plaintext note field.

When you create or update an opportunity:

Providing note_html makes it the source of truth. The plaintext note is automatically derived from it, overriding any note sent in the same request.
On update, sending note_html: null clears both note_html and note.
When you send only note and the opportunity already has a note_html, the rich text version is re-derived from the new note.

The note_html field is always included in opportunity responses (it may be null), but is excluded from CSV and JSON exports.