feat: search query utilities and multi-signal scoring

- Add src/search/query-utils.ts with extractSearchTerms, scorePathRelevance,
  kindBonus, detectApiIntent, inferRouteDirectories
- Add multi-signal scoring to searchNodes (kind bonus + path relevance)
- Improve FTS query sanitization (strip :^ chars, filter boolean operators)
- Add comprehensive search tests

src/search/query-utils.ts

@@ -0,0 +1,129 @@
+/**
+ * Search Query Utilities
+ *
+ * Shared module for search term extraction, scoring, and intent detection.
+ */
+
+import * as path from 'path';
+import { Node } from '../types';
+
+/**
+ * Common stop words to filter from search queries
+ */
+export const STOP_WORDS = new Set([
+  'the', 'a', 'an', 'and', 'or', 'but', 'in', 'on', 'at', 'to', 'for',
+  'of', 'with', 'by', 'from', 'is', 'it', 'that', 'this', 'are', 'was',
+  'be', 'has', 'had', 'have', 'do', 'does', 'did', 'will', 'would', 'could',
+  'should', 'may', 'might', 'can', 'shall', 'not', 'no', 'all', 'each',
+  'every', 'how', 'what', 'where', 'when', 'who', 'which', 'why',
+  'i', 'me', 'my', 'we', 'our', 'you', 'your', 'he', 'she', 'they',
+  'find', 'show', 'get', 'list', 'give', 'tell',
+]);
+
+/**
+ * Extract meaningful search terms from a natural language query
+ */
+export function extractSearchTerms(query: string): string[] {
+  return query
+    .toLowerCase()
+    .replace(/[^\w\s-]/g, ' ')
+    .split(/\s+/)
+    .filter(term => term.length > 1 && !STOP_WORDS.has(term));
+}
+
+/**
+ * Score path relevance to a query
+ * Higher score = more relevant path
+ */
+export function scorePathRelevance(filePath: string, query: string): number {
+  const terms = extractSearchTerms(query);
+  if (terms.length === 0) return 0;
+
+  const pathLower = filePath.toLowerCase();
+  const fileName = path.basename(filePath).toLowerCase();
+  const dirName = path.dirname(filePath).toLowerCase();
+  let score = 0;
+
+  for (const term of terms) {
+    // Exact filename match (strongest)
+    if (fileName.includes(term)) score += 10;
+    // Directory match
+    if (dirName.includes(term)) score += 5;
+    // General path match
+    else if (pathLower.includes(term)) score += 3;
+  }
+
+  return score;
+}
+
+/**
+ * Kind-based bonus for search ranking
+ * Functions and classes are typically more relevant than variables/imports
+ */
+export function kindBonus(kind: Node['kind']): number {
+  const bonuses: Record<string, number> = {
+    function: 10,
+    method: 10,
+    class: 8,
+    interface: 7,
+    type_alias: 6,
+    struct: 6,
+    trait: 6,
+    enum: 5,
+    component: 8,
+    route: 9,
+    module: 4,
+    property: 3,
+    field: 3,
+    variable: 2,
+    constant: 3,
+    import: 1,
+    export: 1,
+    parameter: 0,
+    namespace: 4,
+    file: 0,
+    protocol: 6,
+    enum_member: 3,
+  };
+  return bonuses[kind] ?? 0;
+}
+
+/**
+ * Detect if a query has API/endpoint intent
+ */
+export function detectApiIntent(query: string): boolean {
+  const apiPatterns = [
+    /\bapi\b/i, /\bendpoint/i, /\broute/i, /\bhandler/i,
+    /\bcontroller/i, /\bmiddleware/i, /\brest\b/i, /\bgraphql/i,
+    /\bget\s+\//, /\bpost\s+\//, /\bput\s+\//, /\bdelete\s+\//,
+    /\brequest/i, /\bresponse/i, /\bhttp/i,
+  ];
+  return apiPatterns.some(p => p.test(query));
+}
+
+/**
+ * Infer route/controller directories from project structure
+ * Returns undefined if no route directories are detected
+ */
+export function inferRouteDirectories(files: string[]): string[] | undefined {
+  const routeDirs = new Set<string>();
+  const routePatterns = [
+    /routes?\//i, /controllers?\//i, /handlers?\//i,
+    /api\//i, /endpoints?\//i,
+  ];
+
+  for (const file of files) {
+    for (const pattern of routePatterns) {
+      if (pattern.test(file)) {
+        const match = file.match(pattern);
+        if (match) {
+          const idx = file.indexOf(match[0]);
+          const dir = file.substring(0, idx + match[0].length - 1);
+          routeDirs.add(dir);
+        }
+      }
+    }
+  }
+
+  return routeDirs.size > 0 ? Array.from(routeDirs) : undefined;
+}