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/neural/naturalLanguageProcessor.ts

@@ -99,7 +99,7 @@ export class NaturalLanguageProcessor {
   
   /**
    * Initialize embeddings for all NounTypes and VerbTypes
-   * PRODUCTION OPTIMIZATION (v3.33.0): Uses pre-computed type embeddings
+   * PRODUCTION OPTIMIZATION: Uses pre-computed type embeddings
    * Zero runtime cost - embeddings are loaded instantly from embedded data
    */
   private async initializeTypeEmbeddings(): Promise<void> {