fix(counts): counts.byType() returns inflated values due to accumulation bug

Two critical issues fixed:

1. MetadataIndex.lazyLoadCounts() - Added counts to existing Map instead of
   replacing. Each app restart caused counts to double, leading to 100x
   inflation after ~100 restarts.

2. MetadataIndex.rebuild() and GraphAdjacencyIndex.rebuild() - Did not clear
   count Maps before rebuilding, causing accumulation.

Changes:
- Clear totalEntitiesByType, entityCountsByTypeFixed, verbCountsByTypeFixed
  at start of lazyLoadCounts()
- Clear totalEntitiesByType, entityCountsByTypeFixed, verbCountsByTypeFixed,
  typeFieldAffinity in MetadataIndex.rebuild()
- Clear relationshipCountsByType in GraphAdjacencyIndex.rebuild()

Reported by: Soulcraft Workshop Team

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/graph/graphAdjacencyIndex.ts

@@ -568,6 +568,8 @@ export class GraphAdjacencyIndex {
       // Clear current index
       this.verbIdSet.clear()
       this.totalRelationshipsIndexed = 0
+      // v6.2.4: CRITICAL FIX - Clear relationship counts to prevent accumulation
+      this.relationshipCountsByType.clear()
 
       // Note: LSM-trees will be recreated from storage via their own initialization
       // Verb data will be loaded on-demand via UnifiedCache