Fix version picker to preserve hash and redirect root build to versioned URL

[chinmaymk]

Summary

This PR improves the version picker behavior in the documentation site by preserving URL fragments when switching versions and automatically redirecting users from the root build to the canonical versioned URL.

Key Changes

• Preserve URL hash when switching versions: Modified the onChange() function to include window.location.hash in the target URL and only navigate if the target differs from the current location
• Add root build detection: Introduced isRootBuild() function to identify when users are on the root /ra/ build (not under /dev/ or /v/ paths)
• Auto-redirect root build to versioned URL: When the page loads on the root build, the version picker now automatically redirects to the canonical versioned URL using the latest release version, ensuring the picker stays synchronized with the address bar

Implementation Details

• The hash preservation prevents loss of anchor links when users switch between documentation versions
• The root build redirect uses window.location.replace() to avoid adding an extra history entry
• The redirect only occurs after successfully fetching the versions list and confirming a latest version exists

https://claude.ai/code/session_01WY3WpfMhNfZvMULb8NVzxz