Boost: Fix JITM rendering above header on cache debug log page

[CGastrell]

Proposed changes

• Add #jp-admin-notices JITM slot to the Boost cache debug log page, inside jb-dashboard > jb-container, matching the same structure used on the main Boost page (speed-score.tsx).
• Without this, JITMs injected by the JITM JS render above the page header (in #wpbody-content) instead of below it.

Other information

• Generate changelog entries for this PR (using AI).

Related product discussion/links

• Follows the JITM placement pattern from Fix admin notices and JITMs rendering inside page headers #47558 (Social, My Jetpack, Search)
• Part of the admin page header normalization initiative (Normalize admin page headers with unified AdminHeader wrapping @wordpress/admin-ui #47313)

Does this pull request change what data or activity we track or use?

No.

Testing instructions

Setup: Fake JITM

Add the following snippet to a mu-plugin (e.g. wp-content/mu-plugins/fake-jitm.php) — see #47558 for the full snippet.

Test

1. Go to Jetpack > Boost (wp-admin/admin.php?page=jetpack-boost)
2. Navigate to the Cache debug log page (#/cache-debug-log)
3. Verify the JITM appears below the breadcrumb header, not above it
4. Compare with the main Boost page — JITM placement should be consistent

[github-actions]

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[jp-launch-control]

Code Coverage Summary

This PR did not change code coverage!

That could be good or bad, depending on the situation. Everything covered before, and still is? Great! Nothing was covered before? Not so great. 🤷

Full summary · PHP report · JS report

_{Coverage check overridden by Coverage tests to be added later Use to ignore the Code coverage requirement check when tests will be added in a follow-up PR .}