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

src/types/brainy.types.ts

@@ -789,25 +789,71 @@ export interface NeuralAnomalyParams {
   returnScores?: boolean    // Return anomaly scores
 }
 
+// ============= Content Extraction Types (v7.9.0) =============
+
+/**
+ * Detected content type for smart text extraction
+ *
+ * @since v7.9.0
+ */
+export type ContentType = 'plaintext' | 'richtext-json' | 'html' | 'markdown'
+
+/**
+ * Content category for extracted segments
+ *
+ * Allows UI to apply different styling based on content role:
+ * - 'prose': Regular text content (paragraphs, list items)
+ * - 'heading': Heading/title text (h1-h6)
+ * - 'code': Code blocks or inline code
+ * - 'label': Labels, captions, or metadata-like text
+ *
+ * @since v7.9.0
+ */
+export type ContentCategory = 'prose' | 'heading' | 'code' | 'label'
+
+/**
+ * A segment of extracted text with its content category
+ *
+ * @since v7.9.0
+ */
+export interface ExtractedSegment {
+  /** The extracted text content */
+  text: string
+  /** What role this text plays in the document */
+  contentCategory: ContentCategory
+}
+
 // ============= Semantic Highlighting Types (v7.8.0) =============
 
 /**
- * Parameters for hybrid highlighting (v7.8.0)
+ * Parameters for hybrid highlighting (v7.8.0, enhanced v7.9.0)
  *
  * Zero-config highlighting that returns both text (exact) and semantic (concept) matches.
  * Perfect for UI highlighting at different levels.
  *
+ * v7.9.0: Added contentType hint and contentExtractor callback for structured text
+ * (rich-text JSON, HTML, Markdown). Auto-detects format when not specified.
+ *
  * @example
  * ```typescript
+ * // Plain text (unchanged from v7.8.0)
  * const highlights = await brain.highlight({
  *   query: "david the warrior",
  *   text: "David Smith is a brave fighter who battles dragons"
  * })
- * // Returns: [
- * //   { text: "David", score: 1.0, position: [0, 5], matchType: 'text' },      // Exact match
- * //   { text: "fighter", score: 0.78, position: [25, 32], matchType: 'semantic' }, // Concept match
- * //   { text: "battles", score: 0.72, position: [37, 44], matchType: 'semantic' }  // Concept match
- * // ]
+ *
+ * // Rich-text JSON (auto-detected)
+ * const highlights = await brain.highlight({
+ *   query: "david the warrior",
+ *   text: JSON.stringify(tiptapDocument)
+ * })
+ *
+ * // Custom extractor (for proprietary formats)
+ * const highlights = await brain.highlight({
+ *   query: "function",
+ *   text: sourceCode,
+ *   contentExtractor: (text) => treeSitterParse(text)
+ * })
  * ```
  */
 export interface HighlightParams {
@@ -822,6 +868,21 @@ export interface HighlightParams {
 
   /** Minimum semantic similarity score for semantic matches (default: 0.5) */
   threshold?: number
+
+  /**
+   * Optional content type hint to skip auto-detection.
+   * When omitted, the content type is detected from the text content.
+   * @since v7.9.0
+   */
+  contentType?: ContentType
+
+  /**
+   * Optional custom content extractor function.
+   * When provided, bypasses built-in detection and extraction entirely.
+   * Use this to plug in custom parsers (tree-sitter, Monaco, proprietary formats).
+   * @since v7.9.0
+   */
+  contentExtractor?: (text: string) => ExtractedSegment[]
 }
 
 /**
@@ -843,6 +904,13 @@ export interface Highlight {
 
   /** Match type: 'text' (exact word match) or 'semantic' (concept match) */
   matchType: 'text' | 'semantic'
+
+  /**
+   * Content category of the source segment (heading, code, prose, label).
+   * Present when the input text was structured (JSON, HTML, Markdown).
+   * @since v7.9.0
+   */
+  contentCategory?: ContentCategory
 }
 
 // ============= Export all types =============