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/embeddings/wasm/modelLoader.ts

@@ -1,7 +1,7 @@
 /**
  * Universal Model Loader for Candle Embeddings
  *
- * v7.2.0: Model weights are now loaded separately from WASM for faster initialization.
+ * Model weights are now loaded separately from WASM for faster initialization.
  * This reduces WASM compilation time from 139 seconds to ~3-5 seconds.
  *
  * Loads model files from appropriate source based on environment: