Rich text editing for the threat model context fields

**Context:** The business, technology, and environment context fields are plain text, so a paragraph renders as one unbroken line in a report. Customers documenting for EU CRA compliance write real prose there and it reads badly. From the 2026-08-22 sync.
**Done looks like:** The context fields accept at least bold, italic, and lists, and reports render the formatting.

From the [2026-08-22 maintainer sync](https://github.com/precogly/precogly/discussions/373).

Start with the business, technology, and environment context fields, then trace how their content is included in reports. Check the existing editor and report-rendering entry points before choosing an approach for formatting. Done means those fields accept bold, italic, and lists, and reports preserve that formatting.

Written by the indexing model from the issue text.