Editor: Restore Document Overview after closing Inserter

[dpmehta]

What?

Closes #53078

This PR restores the Document Overview sidebar after the Block Inserter is closed, when Document Overview was open before the Inserter was opened.

Why?

Previously, opening the Inserter from an open Document Overview cleared the List View state. When the Inserter was closed, the entire left sidebar disappeared, causing layout shift and forcing users to reopen Document Overview manually.

How?

• Added an internal hidden state for the List View panel while it is temporarily replaced by the Inserter.
• Restored the List View panel when the Inserter closes if it was open before the Inserter was opened.
• Updated isListViewOpened() so it only reports true when the List View is actually visible.

Testing Instructions

1. Open the editor.
2. Open Document Overview from the top toolbar.
3. Click the top-left Block Inserter button.
4. Close the Inserter using the x button.
5. Confirm Document Overview is restored instead of the left sidebar closing completely.

Also verify:

1. Open the Block Inserter when Document Overview was not open.
2. Close the Inserter.
3. Confirm the left sidebar closes as before.

Screenshots or Screencast

Before Fix :

TreePane.open.-.InserterPane.opened.closed.-.TreePane.gone.-.User.disoriented.mp4

After Fix :

after-fix.mov

Use of AI Tools

Initial technical analysis and PR documentation for this fix were drafted with the assistance of AI tools.

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