Hide topics with 2 or fewer sources from A-Z, category browse, and Google [sc-45176]

[nsantacruz]

Summary

• Topics with ≤2 sources no longer appear on the Topic A-Z page, category/TOC browse cards, or in Google (excluded from topics-sitemap.xml and marked noindex on their own page).
• They remain fully intact in the database and still show up in other topics' "Related Topics" sidebars, as required — the sidebar path (annotate_topic_link) is untouched.
• The existing curation exemption is preserved: a topic with ≤2 sources but a published description or data_source == "sefaria" still displays.
• Topic.should_display() gains an optional min_sources param (default 1, preserving prior behavior everywhere it isn't explicitly overridden); the stricter threshold (MIN_SOURCES_FOR_TOPIC_DISPLAY = 3) is applied only at the three affected call sites: get_all_topics() (A-Z page), get_topic_toc_json_recursive() (category browse), and generate_topics_sitemap().
• No frontend changes needed — the React components already key off the server-computed shouldDisplay field.

Test plan

• pytest sefaria/model/tests/topic_test.py sefaria/helper/tests/topic_test.py — 33 passed, including new coverage for the threshold, the curation exemption, and get_all_topics(min_sources=...)
• Confirmed two pre-existing, unrelated failures in reader/tests/social_image_api_test.py (ALLOWED_HOSTS/hostname handling) are present on master too, via git stash
• Manual verification in a running environment: confirm a ≤2-source topic disappears from /topics/all/<letter> and its category page, still renders directly at /topics/<slug> with <meta name="robots" content="noindex, nofollow">, still appears in a linked topic's sidebar, and is absent from topics-sitemap.xml

🤖 Generated with Claude Code

[gitvelocity-reviewer]

📊 Code Quality Score: 16/100

Base Score 40 × ESF 0.4 = 16

Category	Score	Factors
🔭 Scope	10/20	8 files across model/helper/view/sitemap/constants/tests; single feature applied to multiple surfaces; no new endpoints or DB migrations; contained within topic subsystem
🏗️ Architecture	6/20	Centralizes implicit threshold into named constant; refactors should_display to accept parameter; min_sources_for_display passed via kwargs following existing pattern; no new dependencies
⚙️ Implementation	7/20	Straightforward parameter threading; clean >= vs > equivalence at default; cache key behavior handled by framework; no complex algorithms
⚠️ Risk	6/20	Changes SEO behavior (noindex) for existing pages; modifies sitemap content; changes A-Z listing API response; easily reversible via constant change; no DB migrations or auth changes
✅ Quality	10/15	Good unit tests for should_display covering all branches including exemptions; integration test for get_all_topics; missing tests for view noindex, sitemap, and TOC path; helpful inline comments
🔒 Perf / Security	1/5	Cache behavior considered in tests; no security implications; no performance benchmarks

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