Jetpack Newsletter: Issue with email frequency changes and Subscribe block

### Impacted plugin

Jetpack

### Quick summary

When a user has default notifications set to "Never Send Email," the user remains in a pending subscription state when they subscribe to a blog, which causes issues with the Subscribe block. It does not show the user as subscribed.

If the user is in a pending subscription state when they click on the Subscribe button, they receive a success message, but the button does not change to "subscribed," which does not seem like good UX. Additionally, no email is sent to the user, so the user is not aware of what is happening.

The same thing happens if the user is subscribed to a site and disables the "Email me new posts" setting for that site. They are put in the pending state and the above issue happens again.

---

There is also an issue on the pending subscriptions page `https://wordpress.com/reader/subscriptions/pending`. The site is displaying the .wordpress.com subdomain instead of the main site domain.

### Steps to reproduce

1. Create a site on https://jurassic.ninja/
2. Connect Jetpack
3. Enable Newsletters on `/wp-admin/admin.php?page=jetpack#newsletter`
4. Add the Jetpack Subscribe block to a page
5. Go to https://wordpress.com/me/notifications/subscriptions and set "Default email delivery" to "Never send email"
6. Use the Subscribe block
7. You will get the Success Message, but the Subscribe button will remain the same (will not show as subscribed) and you will be set in a pending subscription state

---
1. Create a site on https://jurassic.ninja/
2. Connect Jetpack
3. Enable Newsletters on `/wp-admin/admin.php?page=jetpack#newsletter`
4. Add the Jetpack Subscribe block to a page
5. Go to https://wordpress.com/me/notifications/subscriptions and set "Default email delivery" to "Deliver email instantly"
6. Use the Subscribe block - You will be subscribed
7. Go to https://wordpress.com/reader/subscriptions
8. Disable "Email me new posts"
9. Go back to the site and delete the `wp-jp-premium-content-session` cookie
10. Try to subscribe again
11. You will get the Success Message, but the Subscribe button will remain the same (will not show as subscribed) and you will be set in a pending subscription state

### Site owner impact

Fewer than 20% of the total website/platform users

### Severity

Moderate

### 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)

_No response_

Reproduce the flow through the Jetpack Subscribe block, /wp-admin/admin.php?page=jetpack#newsletter, the notification subscription settings, and the pending subscriptions page. Compare behavior after changing email delivery from "Never send email" or disabling "Email me new posts." Done means the button and subscription state agree, the user receives appropriate feedback, and the pending page shows the main site domain.

Written by the indexing model from the issue text.