Fetch blob + inline blame without page full refresh

Summary

The following discussion from !219677 (merged) should be addressed:

• @jerasmus started a discussion:

  suggestion (non-blocking): in future iterations we could fetch/re-render the blob + blame inline without a full refresh. I think it would be a nice performance improvement.

When users toggle between Code and Blame views on the blob page, clicking the "View blame prior to this change" link triggers a full page refresh. This causes:

• Slower navigation - the entire page reloads instead of just updating the content
• Loss of scroll position - users lose their place in the file
• Jarring UX - the page flashes and resets state during transitions

Proposed Solution

Fetch blob and blame data inline via API and re-render the content without a full page refresh.