MarkdownContentViewer.tsx exported the isSafeUrl helper alongside the
component so it could be unit tested, which tripped
react-refresh/only-export-components.
Move the helper into a sibling pure module, markdownUrlSafety.ts,
following the existing GraphWorkspace convention for testable non-component
logic (graphAnalytics.ts, pluginRegistryPredicates.ts,
temporalLifecyclePredicates.ts). The function body is moved verbatim — the
scheme allowlist, protocol-relative rejection, whitespace-only guard and
malformed-URL handling are unchanged — so the existing URL-safety tests pass
untouched apart from the import path.
The component module now exports only its component and prop type, clearing
the lint error without any change to the lint configuration.
Co-authored-by: Pravit Ampapathini <pravit.amp@gmail.com>
