Add tests for kg, nlp, web-search, and ask modules

Cover the DQL/knowledge-graph code paths (dql params, raw output, parallel
fan-out, ontology refresh) plus the previously untested option branches in
entities(), webSearch(), and the ask() streaming/error/text-fallback paths.

Raises overall coverage from ~76% to ~83% statements. Adds @vitest/coverage-v8
and a test:coverage script.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: shixish

package.json

@@ -26,6 +26,7 @@
     "test": "vitest run",
     "test:watch": "vitest",
     "test:live": "vitest run --config vitest.live.config.ts",
+    "test:coverage": "vitest run --coverage --coverage.include='src/**'",
     "typecheck": "tsc --noEmit"
   },
   "keywords": [
@@ -41,6 +42,7 @@
   "license": "MIT",
   "devDependencies": {
     "@types/node": "^22.15.21",
+    "@vitest/coverage-v8": "^3.2.6",
     "tsup": "^8.5.0",
     "typescript": "^5.8.3",
     "vitest": "^3.2.1"