chore(8.0): Phase C + D + E — config simplification, TODO sweep, test race fix

Phase C: storageAutoConfig.ts rewrite (376 LOC → ~110 LOC). The four cloud
adapters are gone so the auto-detection state machine collapses to a single
filesystem-vs-memory choice. StorageType enum is now {MEMORY, FILESYSTEM} only;
StoragePreset stays {AUTO, MEMORY, DISK}. zeroConfig.ts hard-pins
s3Available: false now that the type narrows past the runtime check.

Phase D: TODO/FIXME sweep in src/. Removed seven stale markers. The CLI cow
migrate command's backup path now uses fs.cp with recursive + force:false
instead of a TODO placeholder.

Phase E: skipped-test deletion + parallel-test race fix.
  - storage-batch-operations.test.ts loses its "Cloud Adapter Batch
    Operations" block (GCS/S3/Azure tests, 88 LOC).
  - cow-full-integration.test.ts loses its skipped "S3 adapter" test.
  - create-entities-default.test.ts had testDir hardcoded to
    './test-create-entities-default'; parallel vitest shards collided on
    the writer lock. testDir is now os.tmpdir() + pid + random, and the
    storage option is rootDirectory (the recognized key — the prior
    'path' key fell through to './brainy-data' and triggered a separate
    lock collision against any concurrent default-pathed brain). Added
    afterEach brain.close() so the lock releases before rmSync.

tests/unit/create-entities-default.test.ts

@@ -12,10 +12,14 @@ import * as path from 'path'
 
 describe('createEntities Default Value (v4.3.2 Bug Fix)', () => {
   let brain: Brainy
-  const testDir = './test-create-entities-default'
+  // Unique testDir per test invocation so parallel vitest shards don't fight
+  // over the same writer lock on filesystem storage.
+  const testDir = path.join(
+    require('os').tmpdir(),
+    `brainy-create-entities-default-${process.pid}-${Math.random().toString(36).slice(2)}`
+  )
 
   beforeEach(async () => {
-    // Clean up test directory
     if (fs.existsSync(testDir)) {
       fs.rmSync(testDir, { recursive: true })
     }
@@ -23,14 +27,18 @@ describe('createEntities Default Value (v4.3.2 Bug Fix)', () => {
     brain = new Brainy({ requireSubtype: false,
       storage: {
         type: 'filesystem',
-        path: testDir
+        rootDirectory: testDir
       }
     })
     await brain.init()
   })
 
-  afterEach(() => {
-    // Clean up test directory
+  afterEach(async () => {
+    // Release the writer lock before cleaning up the directory, otherwise
+    // parallel vitest shards see a stale lockfile on retry.
+    if (brain) {
+      try { await brain.close() } catch { /* noop */ }
+    }
     if (fs.existsSync(testDir)) {
       fs.rmSync(testDir, { recursive: true })
     }