Editorial Notes: Fix block selection when Show Template is active

[Infinite-Null]

What?

Closes: #1052

Ensures Editorial Notes analyzes the actual post and page content blocks instead of the surrounding template blocks when the "Show template" option is enabled in the WordPress block editor.

Why?

When "Show template" is turned on in WordPress, the editor wraps the post inside template elements (such as the Header, Post Title, Featured Image, and Footer). Editorial Notes was fetching blocks from the root of the template rather than the post content itself. As a result, it only reviewed the template blocks (e.g., 4 blocks) instead of the actual post blocks (e.g., 14 blocks).

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Sonnet 4.6
Used for: Validating bug, suggesting a fix.

Testing Instructions

1. Enable the Editorial Notes experiment under AI > Experiments.
2. Open or create a post with several paragraphs, headings, and lists.
3. With "Show template" turned off, click Generate Editorial Notes in the Post sidebar. Confirm that it reviews all blocks in the post.
4. In the editor header/options, enable Show template.
5. Click Generate Editorial Notes again.
6. Verify that it still reviews the full count of post blocks, rather than just the template blocks.

Screenshots or screencast

Before	After

Changelog Entry

Fixed - Editorial Notes only reviewing template blocks when "Show template" mode is enabled in the block editor.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.87%. Comparing base (5d0efa5) to head (70ecc12).
⚠️ Report is 8 commits behind head on develop.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #1053      +/-   ##
=============================================
+ Coverage      80.72%   80.87%   +0.15%     
  Complexity      2998     2998              
=============================================
  Files            124      124              
  Lines          11978    11987       +9     
=============================================
+ Hits            9669     9695      +26     
+ Misses          2309     2292      -17     

Flag	Coverage Δ
unit	80.87% <ø> (+0.15%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: Infinite-Null <ankitkumarshah@git.wordpress.org>
Co-authored-by: dkotter <dkotter@git.wordpress.org>
Co-authored-by: yogeshbhutkar <yogeshbhutkar@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[yogeshbhutkar]

Adding a few minor nits:

[Infinite-Null]

Hi @dkotter and @yogeshbhutkar, I've addressed all the feedback. Can you please have a look at your convenience. Thank you!

[yogeshbhutkar]

Tests well. Looping @dkotter for another look.

[Infinite-Null]

Just an FYI, I have added a test that is: Displays error notice when post content block is missing from the template for wider test coverage.

cc: @yogeshbhutkar @dkotter