fix(docs): escape braces in tool/trigger description prose for MDX

Tool and trigger descriptions can contain URL path placeholders like
{reportId} or JSON-shape hints like { Items, NextPage }. When rendered
as MDX prose (not table cells), these were emitted unescaped and MDX
parsed them as JSX expressions, failing prerender with
"ReferenceError: reportId is not defined".

Escape { and } in the operation-level description and trigger
description renderers, matching the existing escaping in table-cell
descriptions.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: waleedlatif1