fix: Hide default carousel on subject pages with associated Tags

[SAYAN02-DEV]

Closes #11381

Fix: Exclude default carousel from subject pages when associated with a Tag

Technical

This PR modifies the subject page template to conditionally render the default QueryCarousel based on whether the subject has an associated Tag object.

Changes:

• Modified /openlibrary/templates/subjects.html
• Wrapped the QueryCarousel macro call in an $else block
• The carousel now only renders when has_tag is False (i.e., when 'tag' not in page)
• When a subject has an associated Tag, only the Tag's curated body content is displayed

Testing

1. Subject WITHOUT Tag: Visit /subjects/love - carousel should display
2. Subject WITH Tag: Create a Tag for any subject as admin/curator - carousel should be hidden, only Tag body content shows
3. Verify other page sections (publishing history, related subjects, authors) still appear in both cases

[Copilot]

Pull Request Overview

This PR modifies the subjects page template to conditionally display a default QueryCarousel only when a subject doesn't have an associated Tag. Previously, the QueryCarousel was shown unconditionally regardless of whether the subject had a tag or not.

• Wraps the QueryCarousel in an $else block to prevent it from showing when a tag with custom body content exists
• Adds a clarifying comment explaining the conditional logic

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[jimchamp]

Thanks @SAYAN02-DEV.