refactor(8.0): delete DataAPI — superseded by Db persist/restore + import API + stats

The legacy backup/import/export/stats facade (src/api/DataAPI.ts) drifted
from the modern entity shape and every job it did now has a first-class
surface. Delete it and brain.data(), and rewire the CLI:

- data-stats → brain.stats() (full BrainyStats report: per-type breakdowns,
  indexed fields, index health, storage backend, writer lock, version)
- clean → brain.clear()
- export → alias of snapshot; a db.persist() snapshot is the full-fidelity
  export format (open with Brainy.load, load wholesale with brainy restore);
  external data ingestion remains brainy import (UniversalImportAPI)

Rewiring clean onto brain.clear() exposed two real bugs, both fixed:

- clear() left this.graphIndex undefined forever — any graph-touching call
  afterwards (relate, getNeighbors, stats) crashed. clear() now re-resolves
  the graph index exactly as init() does and re-wires the shared UUID↔int
  resolver, and re-resolves the metadata index with the same provider
  fallback as init().
- storage.clear() reset the legacy totals but not the per-type/subtype
  count rollups or id→type caches, so stats() reported phantom counts for
  deleted entities. Both adapters now delegate derived-state reset to
  reloadDerivedState(), the same path restore-from-snapshot uses.

One-shot CLI commands (data-stats, clean, snapshot/export, restore,
history, generation) now close the brain and exit explicitly — global
cache timers otherwise keep the process alive holding the writer lock.

Verified: build clean, 1383/1383 unit tests, 24/24 db-mvcc integration,
plus an end-to-end CLI smoke (add → data-stats → export → clean →
data-stats).

src/storage/adapters/fileSystemStorage.ts

@@ -1404,26 +1404,15 @@ export class FileSystemStorage extends BaseStorage {
     if (await this.directoryExists(casDir)) {
       // Delete the entire _cas/ directory (not just contents)
       await fs.promises.rm(casDir, { recursive: true, force: true })
-
-      // Drop the BlobStorage instance — its LRU cache holds deleted blobs.
-      // initializeBlobStorage() re-creates it (brain.clear() does this before
-      // the VFS is rebuilt).
-      this.blobStorage = undefined
     }
 
-    // Clear the statistics cache
-    this.statisticsCache = null
-    this.statisticsModified = false
-
-    // Reset entity counters (inherited from BaseStorageAdapter)
-    // These in-memory counters must be reset to 0 after clearing all data
-    ;(this as any).totalNounCount = 0
-    ;(this as any).totalVerbCount = 0
-
-    // Clear write-through cache (inherited from BaseStorage)
-    // Without this, readCanonicalObject() would return stale cached data
-    // after clear(), causing "ghost" entities to appear
-    this.clearWriteCache()
+    // Reset ALL shared derived state via the same path restore uses: the
+    // write-through cache, id→type/subtype caches, per-type/subtype count
+    // rollups, statistics cache, graph-index singleton, and the BlobStorage
+    // instance (its LRU cache holds deleted blobs), then recount from the
+    // now-empty data area. Without the rollup reset, stats() would keep
+    // reporting per-type counts for deleted entities.
+    await this.reloadDerivedState()
   }
 
   /**

src/storage/adapters/memoryStorage.ts

@@ -353,24 +353,14 @@ export class MemoryStorage extends BaseStorage {
     this.blobStore.clear()
     this.txLogLines = []
     this.statistics = null
-    this.totalNounCount = 0
-    this.totalVerbCount = 0
-    this.entityCounts.clear()
-    this.verbCounts.clear()
 
-    // Clear the statistics cache
-    this.statisticsCache = null
-    this.statisticsModified = false
-
-    // Drop the BlobStorage instance — its LRU cache holds deleted blobs.
-    // initializeBlobStorage() re-creates it (brain.clear() does this before
-    // the VFS is rebuilt).
-    this.blobStorage = undefined
-
-    // Clear write-through cache (inherited from BaseStorage)
-    // Without this, readCanonicalObject() would return stale cached data
-    // after clear(), causing "ghost" entities to appear
-    this.clearWriteCache()
+    // Reset ALL shared derived state via the same path restore uses: the
+    // write-through cache, id→type/subtype caches, per-type/subtype count
+    // rollups, statistics cache, graph-index singleton, and the BlobStorage
+    // instance (its LRU cache holds deleted blobs), then recount from the
+    // now-empty object store. Without the rollup reset, stats() would keep
+    // reporting per-type counts for deleted entities.
+    await this.reloadDerivedState()
   }
 
   /**