feat: add structured content extraction and batch embedding optimization to highlight()

Fix highlight() hanging on structured text input by addressing 3 root causes:

1. embedBatch() now uses native WASM batch API (single forward pass instead
   of N individual embed() calls via Promise.all)

2. highlight() auto-detects content type (plain text, rich-text JSON, HTML,
   Markdown) and extracts meaningful text segments. Supports TipTap, Slate.js,
   Lexical, Draft.js, and Quill Delta formats. New contentType hint and
   contentExtractor callback for custom parsers.

3. Semantic matching phase has 10s timeout - falls back to text-only matches
   instead of hanging indefinitely.

Also fixes extractTextContent() array check: uses type-based detection
(typeof data[0] === 'number') instead of length-based (data.length > 10)
so arrays of objects are properly indexed for text search.

New types: ContentType, ContentCategory, ExtractedSegment
New fields: HighlightParams.contentType, HighlightParams.contentExtractor,
            Highlight.contentCategory

CHANGELOG.md

@@ -2,6 +2,80 @@
 
 All notable changes to this project will be documented in this file. See [standard-version](https://github.com/conventional-changelog/standard-version) for commit guidelines.
 
+## [7.8.0](https://github.com/soulcraftlabs/brainy/compare/v7.7.0...v7.8.0) (2026-01-27)
+
+### Bug Fixes
+
+**highlight() hangs on structured text input**
+
+Three root causes fixed:
+
+1. **embedBatch() now uses native WASM batch API** — Previously called `embed()` individually N times via `Promise.all`, each creating a separate forward pass. Now delegates to `engine.embedBatch()` for a single WASM forward pass. Applies globally to all `embedBatch()` callers.
+
+2. **Smart content extraction for structured text** — `highlight()` now auto-detects content type (plain text, rich-text JSON, HTML, Markdown) and extracts meaningful text segments instead of splitting raw JSON/HTML into garbage chunks like `{"type":`. Supports TipTap, Slate.js, Lexical, Draft.js, and Quill Delta formats out of the box.
+
+3. **Timeout protection** — Semantic matching phase now has a 10-second timeout. On timeout or error, `highlight()` returns Phase 1 text-only matches (always fast) instead of hanging indefinitely.
+
+**extractTextContent() skips arrays of objects** — Changed from length-based skip (`data.length > 10`) to type-based check (`typeof data[0] === 'number'`). Arrays of objects (e.g., team members, items) are now properly indexed for text search instead of being silently skipped.
+
+### Features
+
+**Structured Content Highlighting**
+
+`highlight()` now handles structured text formats automatically:
+
+```typescript
+// Rich-text JSON (TipTap, Slate, Lexical, Draft.js, Quill)
+const highlights = await brain.highlight({
+  query: "warrior",
+  text: JSON.stringify(tiptapDocument)
+})
+// Each highlight includes contentCategory: 'heading' | 'prose' | 'code' | 'label'
+
+// HTML
+await brain.highlight({ query: "warrior", text: "<h1>Warriors</h1><p>Brave fighters.</p>" })
+
+// Markdown
+await brain.highlight({ query: "warrior", text: "# Warriors\n\nBrave fighters." })
+```
+
+**Content Category Annotations**
+
+Each `Highlight` now includes `contentCategory` when input is structured:
+- `'heading'` — from `<h1>`-`<h6>`, `# Heading`, or heading nodes
+- `'code'` — from `<code>`/`<pre>`, fenced/indented code blocks, or code nodes
+- `'prose'` — regular paragraph text
+- `'label'` — labels, captions, metadata-like text
+
+**Custom Content Extractors**
+
+New `contentExtractor` parameter lets developers plug in custom parsers:
+
+```typescript
+const highlights = await brain.highlight({
+  query: "function",
+  text: sourceCode,
+  contentExtractor: (text) => treeSitterParse(text)  // Custom parser
+})
+```
+
+**Content Type Hints**
+
+New `contentType` parameter to skip auto-detection:
+
+```typescript
+await brain.highlight({ query: "test", text: input, contentType: 'html' })
+```
+
+### New Types
+
+- `ContentType`: `'plaintext' | 'richtext-json' | 'html' | 'markdown'`
+- `ContentCategory`: `'prose' | 'heading' | 'code' | 'label'`
+- `ExtractedSegment`: `{ text: string, contentCategory: ContentCategory }`
+- `HighlightParams.contentType?` — optional content type hint
+- `HighlightParams.contentExtractor?` — optional custom parser callback
+- `Highlight.contentCategory?` — content role annotation
+
 ## [7.7.0](https://github.com/soulcraftlabs/brainy/compare/v7.6.1...v7.7.0) (2026-01-26)
 
 ### Features