detailsFromContext workspaceJson escapes

Trap: extracting [workspace: "..."] with a permissive regex looks sufficient because ordinary quoted names match, but invalid JSON escapes such as cli\qnext still match and make JSON.parse(workspaceJson) throw an unhandled SyntaxError. Fix: wrap that parse in try/catch and convert failures into the module’s contextual validation error, because issue content is untrusted and malformed metadata must fail cleanly.