feat: Enhance search ranking with name matching and field extraction improvements

Adds nameMatchBonus scoring to prioritize results where node names exactly or partially match query terms. Implements dedicated field extraction for Java/C# to properly categorize class fields vs variables. Optimizes BM25 search with column weights favoring name matches and increased result fetching before post-processing. Refines stop words list to preserve common programming terms like "get", "find", "list".

src/extraction/tree-sitter-types.ts

@@ -98,6 +98,8 @@ export interface LanguageExtractor {
   callTypes: string[];
   /** Node types that represent variable declarations (const, let, var, etc.) */
   variableTypes: string[];
+  /** Node types that represent class fields (extracted as 'field' kind inside class bodies) */
+  fieldTypes?: string[];
 
   // --- Field name mappings ---