Preserve mode flags when updating URL

[tristanmanchester]

Summary

• Preserve editor=true when URLManager.updateURL() rewrites application state into the query string.
• Preserve frontend-only=true the same way.
• Delete each flag when the corresponding app mode is false, matching the existing set/delete pattern for markdown, metadata, jmespath, and grid state.

Bug

updateConfigsFromURL() reads editor and frontend-only query parameters to enable editor mode and frontend-only mode, but updateURL() did not write those parameters back out when other state changed. Any action that called updateURL(), such as pagination, markdown/metadata toggles, layout changes, or search, could rewrite the URL without these mode flags.

For editor mode this meant a user could remain in editor mode during the current session, but after refresh the URL no longer contained editor=true, so the app reopened outside editor mode.

Fix

updateURL() now mirrors the read-side URL flags:

• this.app.isEditorMode controls editor=true
• this.app.isFrontendOnlyMode controls frontend-only=true

This keeps mode state stable across normal URL updates while still removing the flags when those modes are disabled.

Verification

• Reviewed updateConfigsFromURL() to confirm both flags are read from the URL.
• Confirmed common app actions call this.urlManager.updateURL(), making the reported stripping path legitimate.
• Ran pnpm run build successfully.