Portfolio slug remains reserved after disabling Portfolio

### Impacted plugin

Jetpack

### Quick summary

After enabling and then disabling `Portfolio` , the /portfolio slug appears to remain permanently reserved. This prevents users from properly restoring a custom page at /portfolio/, and child pages return 404 errors while the "Portfolio" is enabled. Then the parent and child pages redirect to the homepage after disabling the "Portfolio."

**References:**
Similar issues had been previously reported:

* [https://github.com/Automattic/jetpack/issues/995]()
* [https://github.com/Automattic/jetpack/issues/30788]()

### Steps to reproduce

1. While the "Portfolio" is disabled (not previously enabled), create a page with the slug /portfolio.
2. Create child pages, and assign the "Portfolio" page as the parent page.
3. See the parent and child pages work as expected.
4. Enable "Portfolio" on Settings → Writing
5. See the child pages now return a page not found error.
6. Disable "Portfolio" on Settings → Writing and both the parent and child pages of the "Portfolio" page will redirect to the homepage.

### Expected Behavior:

After disabling "Portfolio", the /portfolio slug should become available again for pages and the child pages will work.

### Actual Behavior:

The /portfolio slug stays reserved, and its child pages redirects to the home page.

### Site owner impact

Fewer than 20% of the total website/platform users

### Severity

Critical

### What other impact(s) does this issue have?

*No response*

### If a workaround is available, please outline it here.

*No response*

### Platform (Simple and/or Atomic)

Simple

Start by reproducing the Portfolio enable/disable sequence from the issue through Settings → Writing, focusing on page routing and slug reservation. Trace what happens to the /portfolio parent and its child pages after Portfolio is disabled; done means the slug is available again and both parent and child pages load normally.

Written by the indexing model from the issue text.