fix(8.0): honor top-level storage.path as a rootDirectory alias

`storage: { type: 'filesystem', path: '…' }` is a widely-used, doc-promoted
config shape, but the 8.0 storage refactor dropped top-level `path` from the
root-directory resolution chain — so it was silently ignored and every such
brain wrote to the default `./brainy-data` instead. A consumer upgrading with
`storage: { path: './my-data' }` would have had their data quietly relocated.

Restores `path` as a first-class alias for `rootDirectory` (it already worked
nested under `options.path`; now it works top-level too), adds it to the
StorageOptions / BrainyConfig.storage types, and pins every accepted spelling
(rootDirectory, path, options.rootDirectory, options.path, default) in a unit
test of the resolution chain.

src/storage/storageFactory.ts

@@ -42,6 +42,14 @@ export interface StorageOptions {
   /** Root directory for filesystem storage. */
   rootDirectory?: string
 
+  /**
+   * Alias for `rootDirectory`. The `storage: { type: 'filesystem', path: '…' }`
+   * shape is widely used (and shown throughout the docs), so it is honored as a
+   * first-class top-level key — not silently ignored in favour of the default
+   * directory.
+   */
+  path?: string
+
   /**
    * Nested options block (backward-compat for `BrainyConfig.storage.options`).
    * Recognized keys: `rootDirectory`, `path`.
@@ -94,6 +102,7 @@ async function pickAdapter(options: StorageOptions): Promise<StorageAdapter> {
 async function createFilesystemStorage(options: StorageOptions): Promise<StorageAdapter> {
   const rootDir =
     options.rootDirectory ??
+    options.path ??
     options.options?.rootDirectory ??
     options.options?.path ??
     './brainy-data'

src/types/brainy.types.ts

@@ -1202,6 +1202,9 @@ export interface BrainyConfig {
         /** Root directory for filesystem storage. Passed through to storage factories
          *  including plugin-provided factories (e.g. native mmap providers). */
         rootDirectory?: string
+        /** Alias for `rootDirectory`. The `storage: { type: 'filesystem', path: '…' }`
+         *  shape is honored as a first-class key so existing configs keep working. */
+        path?: string
         options?: any
       }
     | StorageAdapter

tests/unit/storage/storage-path-config.test.ts

@@ -0,0 +1,53 @@
+/**
+ * Storage root-directory resolution from `StorageOptions`.
+ *
+ * `storage: { type: 'filesystem', path: '…' }` is a widely-used, doc-promoted
+ * config shape. A refactor once dropped the top-level `path` key from the
+ * resolution chain, so it was silently ignored and every brain wrote to the
+ * default `./brainy-data` instead — a quiet data-misplacement footgun on
+ * upgrade. These tests pin every accepted spelling to the directory it must
+ * resolve to.
+ */
+import { describe, it, expect } from 'vitest'
+import { createStorage } from '../../../src/storage/storageFactory.js'
+
+/** Read the resolved root directory off the concrete FileSystemStorage. */
+function rootDirOf(storage: unknown): string {
+  return (storage as { rootDir: string }).rootDir
+}
+
+describe('createStorage — filesystem root-directory resolution', () => {
+  it('honors top-level rootDirectory', async () => {
+    const storage = await createStorage({ type: 'filesystem', rootDirectory: '/tmp/brainy-rd' })
+    expect(rootDirOf(storage)).toBe('/tmp/brainy-rd')
+  })
+
+  it('honors top-level path (the documented shorthand)', async () => {
+    const storage = await createStorage({ type: 'filesystem', path: '/tmp/brainy-path' })
+    expect(rootDirOf(storage)).toBe('/tmp/brainy-path')
+  })
+
+  it('honors nested options.rootDirectory', async () => {
+    const storage = await createStorage({ type: 'filesystem', options: { rootDirectory: '/tmp/brainy-ord' } })
+    expect(rootDirOf(storage)).toBe('/tmp/brainy-ord')
+  })
+
+  it('honors nested options.path', async () => {
+    const storage = await createStorage({ type: 'filesystem', options: { path: '/tmp/brainy-opath' } })
+    expect(rootDirOf(storage)).toBe('/tmp/brainy-opath')
+  })
+
+  it('prefers top-level rootDirectory over a nested options.path', async () => {
+    const storage = await createStorage({
+      type: 'filesystem',
+      rootDirectory: '/tmp/brainy-win',
+      options: { path: '/tmp/brainy-lose' }
+    })
+    expect(rootDirOf(storage)).toBe('/tmp/brainy-win')
+  })
+
+  it('falls back to ./brainy-data only when no directory is supplied', async () => {
+    const storage = await createStorage({ type: 'filesystem' })
+    expect(rootDirOf(storage)).toBe('./brainy-data')
+  })
+})