New Experiment: Suggest permalink slugs

What problem does this address?

Well-crafted permalink slugs carry real SEO value (concise, keyword-relevant URLs), but authors often leave the auto-generated slug as-is or hand-edit it without much thought. This is a good candidate for AI assistance, similar in spirit to this plugin's existing Title Generation and Excerpt Generation experiments with their same "one-click, review, apply" pattern, but applied to the permalink slug instead.

What is your proposed solution?

Add a new experiment that suggests a slug for the post permalink based on the post's title and/or content, following the same generate >> review >> select pattern as Title Generation.

Still open, and worth settling with the community before/while scoping this: where the trigger and suggestion(s) surface. A few options, not mutually exclusive:

1. Pre-publish flow: slug suggestion appears as a step in the pre-publish panel, alongside other pre-publish checks.
2. Post editor sidebar, alongside the slug/permalink editing UI: a "Generate/Regenerate" affordance next to the existing slug field, matching how Title Generation surfaces above the title field.
3. Both: sidebar trigger for on-demand use while drafting, pre-publish surfacing as a nudge for anyone who hasn't touched the slug yet.

Scope for v1

• Ability to generate a slug suggestion (or a short list of options) from post title/content.
• Review-and-select only; nothing overwrites the existing slug without the user choosing it, consistent with how every other experiment in this plugin requires explicit user action.
• Filterable: number of suggestions returned, making use of the existing minimum content length requirement before suggestions are offered (similar to the existing content-length gate on Summarization).

Open questions

• Pre-publish panel, sidebar-next-to-slug, or both? See above, this affects where the ability gets wired into the editor UI. [I think starting with just the sidebar-next-to-slug would suffice]
• Should slug suggestions consider existing permalinks on the site to avoid near-duplicate slugs, or is that out of scope for v1?
• Does this warrant a WP-CLI command for bulk slug review/regeneration on existing content, similar to the alt-text bulk command?

Why is this important to you?

No response

I have searched existing issues and this is not a duplicate.

• Yes