What?

Closes #792

For the "Generate Editorial Note" option in Editorial Note experiment:

• Shows the "Reviewing..." loading spinner only on the actual clicked block, instead of showing it on every content block's option menu.
• Displays an additional info for the other blocks stating that a review process is ongoing for another block.

Why?

It solves a visual bug where running an AI review on one block makes it look like every block is being reviewed.

How?

This is address by tracking the specific block ID under review instead of a global true/false state, other blocks correctly show as disabled with an explanation (Another block is currently being reviewed) rather than showing a confusing loading spinner.

• Instead of using a simple isReviewing boolean state, we now track reviewingClientId which stores the ID of the block currently under review / null if none under review.

• This allows to check for isReviewing i.e. any block is under review by evaluating !!reviewingClientId i.e. truthy if a block ID is stored and false if null.

• By comparing reviewingClientId to the current block's ID, we only show the "Reviewing..." text and loading spinner conditionally to the under review block only.

• And for non equality, where we know a review is still occurring, the menu item remains as "Generate Editorial Note" and displays an additional info label of "Another block is currently being reviewed." while staying disabled.

• Added an e2e test to verify the same.

Use of AI Tools

AI assistance: Yes
Tool(s): Antigravity IDE
Model(s): Gemini 3.5 Flash (Low)
Used for: Identifying the relevant files for the fix, suitable resolutions and E2E test implementation. Final implementation and tests were reviewed and edited by me.

Testing Instructions

1. Enable Editorial Note experiment.
2. Open the post editor and insert two paragraph blocks with enough content to run AI Editorial reviews.
3. Select the first block, click the "Options" (three dots) button in the block toolbar, and click "Generate Editorial Note".
4. While the review is running (spinner showing on the first block), select the second block and click its "Options" button in the block toolbar.
5. Observe the menu item for Editorial Notes on the second block:
6. It should display the "Generate Editorial Note" label but disabled, along with helper info text indicating that "Another block is currently being reviewed."

Screenshots or screencast

Changelog Entry

Fixed - Scope the Editorial Note generation loading spinner only to the block currently being reviewed.