feat(8.0)!: delete fork/branch/commit/history/versions — superseded by the Db API

The COW version-control surface (fork, branches, checkout, commit,
getHistory/streamHistory, asOfCommit, brain.versions) is gone, along with
its subsystems: src/versioning/, the COW object store (CommitLog,
CommitObject, RefManager, TreeObject), HistoricalStorageAdapter, and the
TypeAwareHNSWIndex path it kept alive. The Db API (now/transact/asOf/
with/persist/restore) is the one versioning model in 8.0.

Survivors and replacements:
- BlobStorage survives (the VFS stores file content through it), relocated
  to src/storage/blobStorage.ts with binaryDataCodec.ts; its adapter
  interface is now BlobStoreAdapter, slimmed to the consumed surface
  (write/read/has/delete/getMetadata + MIME-aware compression policy).
- brain.migrate() backup branches are replaced by persist-before-migrate:
  MigrateOptions.backupTo persists a hard-link snapshot of the current
  generation before any transform runs; MigrationResult.backupPath reports
  it, and brain.restore(path) brings it back wholesale.
- CLI: cow.ts (fork/branch/checkout/history/migrate) is replaced by
  snapshot.ts — snapshot <path>, restore <path>, history (tx-log),
  generation.
- New public read API: brain.transactionLog({limit}) exposes the reified
  tx-log (generation/timestamp/meta, newest first) that backs the CLI
  history command; TxLogEntry is exported.

Tests: superseded suites deleted; fork/commit blocks excised from shared
suites; BlobStorage tests relocated + reworked against the slimmed store;
migration tests now prove the backupTo snapshot/restore round trip; new
transactionLog coverage in db-mvcc.

tests/integration/storage-batch-operations.test.ts

@@ -1,9 +1,8 @@
 /**
  * Storage-Level Batch Operations Test Suite v5.12.0
  *
- * Comprehensive testing of new storage-level batch APIs:
+ * Comprehensive testing of storage-level batch APIs:
  * - storage.getNounMetadataBatch() - Batch metadata reads
- * - storage.readBatchWithInheritance() - COW-aware batch reads
  * - storage.getVerbsBySourceBatch() - Batch relationship queries
  * - brain.batchGet() - High-level batch entity retrieval
  * - PathResolver.getChildren() - VFS batch operations
@@ -11,10 +10,8 @@
  * Coverage:
  * ✅ Type-aware storage compatibility
  * ✅ Sharding preservation
- * ✅ COW (Copy-on-Write) integration
- * ✅ fork() and branch isolation
+ * ✅ Write-cache coherence
  * ✅ Performance improvements (N+1 → batched)
- * ✅ Cloud adapter native batch APIs
  */
 
 import { describe, it, expect, beforeEach, afterEach } from 'vitest'
@@ -129,13 +126,13 @@ describe('Storage-Level Batch Operations v5.12.0', () => {
   })
 
   describe('storage.getNounMetadataBatch() - Storage Layer', () => {
-    it('should batch fetch noun metadata with type caching', async () => {
+    it('should batch fetch noun metadata across types via ID-first paths', async () => {
       // Add entities of different types
       const id1 = await brain.add({ type: 'document', data: 'Doc' })
       const id2 = await brain.add({ type: 'thing', data: 'Thing' })
       const id3 = await brain.add({ type: 'person', data: 'Person' })
 
-      // Access storage directly
+      // Access storage directly (8.0 layout: ID-first paths, no type lookup)
       const storage = brain.storage as any
       const results = await storage.getNounMetadataBatch([id1, id2, id3])
 
@@ -143,32 +140,18 @@ describe('Storage-Level Batch Operations v5.12.0', () => {
       expect(results.get(id1)?.noun).toBe('document')
       expect(results.get(id2)?.noun).toBe('thing')
       expect(results.get(id3)?.noun).toBe('person')
-
-      // Type cache should be populated
-      expect(storage.nounTypeCache.has(id1)).toBe(true)
-      expect(storage.nounTypeCache.get(id1)).toBe('document')
     })
 
-    it('should handle uncached IDs by trying multiple types', async () => {
-      // Add entity
+    it('should omit missing ids from the result map', async () => {
       const id = await brain.add({ type: 'document', data: 'Test' })
+      const missing = '00000000-0000-4000-8000-000000000000'
 
-      // Clear type cache to simulate uncached scenario
       const storage = brain.storage as any
-      storage.nounTypeCache.delete(id)
-
-      // Batch fetch should still work (tries all types)
-      const results = await storage.getNounMetadataBatch([id])
+      const results = await storage.getNounMetadataBatch([id, missing])
 
       expect(results.size).toBe(1)
       expect(results.get(id)?.noun).toBe('document')
-
-      // Cache should be repopulated (or may still be empty if metadata doesn't populate it)
-      // This is acceptable as long as the data is retrieved correctly
-      const cachedType = storage.nounTypeCache.get(id)
-      if (cachedType !== undefined) {
-        expect(cachedType).toBe('document')
-      }
+      expect(results.has(missing)).toBe(false)
     })
 
     it('should preserve sharding in all paths', async () => {
@@ -212,32 +195,7 @@ describe('Storage-Level Batch Operations v5.12.0', () => {
     })
   })
 
-  describe('COW Integration - readBatchWithInheritance()', () => {
-    it('should resolve branch paths before reading', async () => {
-      // Add entity on main
-      const id = await brain.add({ type: 'document', data: 'Main branch' })
-
-      // Create fork
-      const fork = await brain.fork('test-branch')
-
-      // Add entity on fork
-      const forkId = await fork.add({ type: 'document', data: 'Fork branch' })
-
-      // Batch get on fork should see fork entity
-      const forkResults = await fork.batchGet([forkId, id])
-
-      expect(forkResults.size).toBe(2)
-      expect(forkResults.get(forkId)?.data).toBe('Fork branch')
-      expect(forkResults.get(id)?.data).toBe('Main branch') // Inherited
-
-      // Batch get on main should NOT see fork entity
-      const mainResults = await brain.batchGet([forkId, id])
-
-      expect(mainResults.size).toBe(1)
-      expect(mainResults.has(forkId)).toBe(false) // Not on main
-      expect(mainResults.get(id)?.data).toBe('Main branch')
-    })
-
+  describe('Write-cache coherence', () => {
     it('should respect write cache for dirty entities', async () => {
       // Add entity
       const id = await brain.add({ type: 'document', data: 'Original' })
@@ -250,29 +208,6 @@ describe('Storage-Level Batch Operations v5.12.0', () => {
 
       expect(results.get(id)?.data).toBe('Updated')
     })
-
-    it('should inherit from parent commits for missing entities', async () => {
-      // Add entities on main
-      const id1 = await brain.add({ type: 'document', data: 'Main 1' })
-      const id2 = await brain.add({ type: 'document', data: 'Main 2' })
-
-      // Commit
-      await brain.commit('Initial entities')
-
-      // Create fork
-      const fork = await brain.fork('child-branch')
-
-      // Add new entity only on fork
-      const forkId = await fork.add({ type: 'document', data: 'Fork only' })
-
-      // Batch get on fork should inherit main entities
-      const results = await fork.batchGet([id1, id2, forkId])
-
-      expect(results.size).toBe(3)
-      expect(results.get(id1)?.data).toBe('Main 1') // Inherited
-      expect(results.get(id2)?.data).toBe('Main 2') // Inherited
-      expect(results.get(forkId)?.data).toBe('Fork only') // Fork's own
-    })
   })
 
   describe('getVerbsBySourceBatch() - Batch Relationship Queries', () => {