Show "Generate" instead of "Regenerate" when post body is empty

[i-anubhav-anand]

Problem

Fixes #391

The toolbar button was labelled Regenerate whenever the post had a title, even when the post body was empty. With no content the AI has nothing to work from, so "Regenerate" was misleading — it implied a previous generation existed and would be replaced.

Solution

Read getEditedPostContent() in the useSelect call and only label the button "Regenerate" when the post has both a title and body content. When the body is empty the button always reads Generate, making the prerequisite clear to users.

Changes

• src/experiments/title-generation/components/TitleToolbar.tsx
  • Add content to useSelect return value
  • Derive hasContent from the post body
  • Use hasTitle && hasContent instead of hasTitle to decide the "Regenerate" label
  • Rename content variable inside handleGenerate / handleRegenerate to postContent to avoid shadowing the new reactive state

Testing

1. Create a new post — leave the body empty, add only a title
   • Button should read Generate
2. Add body content
   • Button should switch to Regenerate
3. Clear body content again
   • Button should return to Generate
4. Generate a title with content present — modal Regenerate button should work as before

[github-actions]

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Co-authored-by: i-anubhav-anand <anubhav24@git.wordpress.org>
Co-authored-by: dkotter <dkotter@git.wordpress.org>
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[dkotter]

@i-anubhav-anand This is another PR that duplicates work done in an existing PR (see #479). I'd suggest as you look to pick up Issues, don't work on Issues that already have a PR attached as it just makes things more difficult for maintainers. If you have a different approach to what's already there, that should be a conversation that happens either on that PR or on the Issue first.