Notes: mention notification link opens the post but the Notes panel is hidden behind the default editor sidebar

Description

When a user clicks a deep-link from a Note mention notification email, the correct post opens in the editor and the referenced note is deep-linked in the Notes panel — but the default editor sidebar (document/block settings) is active on page load, visually covering the Notes panel.

From the user's perspective the notification link "opens the post but not the note", because the Notes panel is not visible without manually switching sidebars. The behaviour is correct underneath — the note is focused — it's just obscured by the default sidebar state on entry.

https://github.com/user-attachments/assets/f6aec74b-09b7-4afa-a013-42af058eba63

Steps to reproduce

1. User A mentions user B in a note on a post.
2. User B opens the notification email and clicks the link.
3. Editor opens on the correct post.
4. Observe the sidebar: the default document/block settings sidebar is showing, not the Notes panel.

Expected

When the editor opens via a note-deep-link, the Notes panel is the active sidebar (or otherwise visible) so the referenced note is on-screen immediately.

Actual

The default sidebar covers the Notes panel. The user has to manually open the Notes panel to see the note they were sent to.

Reporter's own words

The link in the Note notification email opens the correct post in the editor, but it does not open the Notes sidebar or focus the specific Note referenced in the notification. I'd expect the link to take the recipient directly to the relevant Note.

Start by tracing the note notification deep-link handling and the editor sidebar initialization described in the reproduction steps. Reproduce the email-link flow and confirm that the referenced post opens with the Notes panel visible and the referenced note on-screen instead of behind the default sidebar.