feat(8.0)!: delete fork/branch/commit/history/versions — superseded by the Db API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Tests: superseded suites deleted; fork/commit blocks excised from shared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.

src/cli/index.ts

@@ -17,7 +17,7 @@ import { storageCommands } from './commands/storage.js'
 import { nlpCommands } from './commands/nlp.js'
 import { insightsCommands } from './commands/insights.js'
 import { importCommands } from './commands/import.js'
-import { cowCommands } from './commands/cow.js'
+import { snapshotCommands } from './commands/snapshot.js'
 import { inspectCommands } from './commands/inspect.js'
 import { readFileSync } from 'fs'
 import { fileURLToPath } from 'url'
@@ -760,58 +760,30 @@ program
   .option('--iterations <n>', 'Number of iterations', '100')
   .action(utilityCommands.benchmark)
 
-// ===== COW Commands - Instant Fork & Branching =====
+// ===== Snapshot & Time-Travel Commands - Db API =====
 
 program
-  .command('fork [name]')
-  .description('🚀 Fork the brain (instant clone in 1-2 seconds)')
-  .option('--message <msg>', 'Commit message')
-  .option('--author <name>', 'Author name')
-  .action(cowCommands.fork)
+  .command('snapshot <path>')
+  .description('📸 Persist the current generation as a self-contained snapshot (instant hard links)')
+  .action(snapshotCommands.snapshot)
 
 program
-  .command('branch')
-  .description('🌿 Branch management')
-  .addCommand(
-    new Command('list')
-      .alias('ls')
-      .description('List all branches/forks')
-      .action((options) => {
-        cowCommands.branchList(options)
-      })
-  )
-  .addCommand(
-    new Command('delete')
-      .alias('rm')
-      .argument('[name]', 'Branch name to delete')
-      .description('Delete a branch/fork')
-      .option('-f, --force', 'Skip confirmation')
-      .action((name, options) => {
-        cowCommands.branchDelete(name, options)
-      })
-  )
-
-program
-  .command('checkout [branch]')
-  .alias('co')
-  .description('Switch to a different branch')
-  .action(cowCommands.checkout)
+  .command('restore <path>')
+  .description('Replace the ENTIRE store state from a snapshot (asks for confirmation)')
+  .option('-f, --force', 'Skip confirmation')
+  .action(snapshotCommands.restore)
 
 program
   .command('history')
   .alias('log')
-  .description('Show commit history')
-  .option('-l, --limit <number>', 'Number of commits to show', '10')
-  .action(cowCommands.history)
+  .description('Show the transaction log (one entry per committed transact() batch)')
+  .option('-l, --limit <number>', 'Number of entries to show', '10')
+  .action(snapshotCommands.history)
 
 program
-  .command('migrate')
-  .description('🔄 Migrate from v4.x to v5.0.0 (one-time)')
-  .option('--from <path>', 'Old Brainy data path (v4.x)')
-  .option('--to <path>', 'New Brainy data path (v5.0.0)')
-  .option('--backup', 'Create backup before migration')
-  .option('--dry-run', 'Show migration plan without executing')
-  .action(cowCommands.migrate)
+  .command('generation')
+  .description('Show the store\'s current generation watermark')
+  .action(snapshotCommands.generation)
 
 // ===== Interactive Mode =====