836b480ea6
A click on a child of an <a> (e.g. nested <strong>, <em>, <code>, icon)
made event.target a non-anchor, so getAttribute('href') returned null
and the handler bailed without preventDefault. The browser then
performed the native navigation, which for relative links like
'../note.md' resolved against the current /:user/:repo URL and the SPA
re-routed treating the destination as a new repo.