Replace byte-chunking with section-based Algolia indexing

[rosieyohannan]

Summary

• Root cause of poor search: The previous indexing split pages at arbitrary byte boundaries (~8,500 bytes), producing ~520 large records with no awareness of document structure. Chunk boundaries fell mid-phrase (e.g. splitting "Pipeline states" across two records), and huge records diluted Algolia relevance scores so the right section ranked below unrelated pages.
• New approach: One Algolia record per h2/h3/h4 section. The section heading is stored in a dedicated heading field with higher search priority than body content. The section anchor (#pipeline-states) is included in the record URL so clicking a result links directly to the right section on the page.
• Expected record count: ~5,000–15,000 (from ~520), average size ~1KB (from ~5.5KB) — matching what the old Algolia crawler produced.
• Search results display: Shows Page title / Section heading so users can see both which page and which section matched.

Changes

extensions/export-content-extension.js

• Replace collectPages + chunkText with section-based extraction using extractSections
• extractSections splits page HTML at h2/h3/h4 boundaries, extracts heading text and id attribute (anchor) per section
• indexToAlgolia simplified: one record per section, no chunking loop
• searchableAttributes updated to [title, heading, content, path] — section heading matches rank above body text

ui/src/js/07-search.js

• Add heading to attributesToRetrieve
• Result title displays as Page title / Section heading when a section heading exists

Test plan

• Run a local build with SKIP_INDEX_SEARCH=true and inspect .temp/site-content.json — records should have heading field and relUrl values with # anchors
• After merge and CI index rebuild: search "pipeline states" — should return the Pipeline states section of the pipelines overview page as a top result
• Verify search result displays as Pipelines overview and setup / Pipeline states
• Verify clicking the result lands on the #pipeline-states anchor
• Check Algolia dashboard record count is substantially higher than 520

🤖 Generated with Claude Code

[linear-code]

DOC-176