fix: exclude __words__ keyword index from corruption detection and getStats()

The __words__ keyword index stores 50-5000 entries per entity (one per
word), which inflated avg entries/entity well above the corruption
threshold of 100. This caused:

1. validateConsistency() to falsely detect corruption on every startup,
   triggering unnecessary clearAllIndexData() + rebuild() cycles
2. getStats() to log false "Metadata index may be corrupted" warnings
   and report inflated totalEntries/totalIds stats

Both methods now skip __words__ when counting, so stats and health
checks reflect metadata fields only (noun, type, createdAt, etc.).
Keyword search is unaffected since the __words__ field index itself
is not modified.

src/integrations/index.ts

@@ -7,7 +7,7 @@
  * - Real-time dashboards (SSE streaming)
  * - External webhooks (push notifications)
  *
- * @example Enable integrations (v7.4.0 - recommended)
+ * @example Enable integrations (recommended)
  * ```typescript
  * import { Brainy } from '@soulcraft/brainy'
  *