SEC-WEB-33: Replace raw diagram source and detailed error messages in
MermaidViewer error UI with a generic "Diagram rendering failed" message.
Detailed errors are logged to console.error for debugging only.
SEC-WEB-35: Add console.warn in useWorkspaceId when no workspace ID is
found in localStorage, making it easier to distinguish "no workspace
selected" from silent hook failure.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
