refactor: remove deprecated BrainyData class completely

Removes all traces of BrainyData to prevent user confusion:
- Renamed brainyDataInterface.ts to brainyInterface.ts for clarity
- Updated all imports and type references across 5 files
- Removed BrainyData compiled artifacts (handled by clean build)
- Added deprecation notice to CHANGELOG with migration guide

BrainyData was never part of official Brainy 3.0 API but existed as
legacy compiled artifacts. Users mistakenly imported it thinking neural
API was missing, when it exists in modern Brainy class.

All users should migrate to: new Brainy() with await brain.init()
Neural API available via: brain.neural().visualize() etc.

Resolves confusion reported by Brain Studio team.

src/shared/default-augmentations.ts

@@ -5,7 +5,7 @@
  * These are the core "sensory organs" of the atomic age brain-in-jar system
  */
 
-import { BrainyInterface } from '../types/brainyDataInterface.js'
+import { BrainyInterface } from '../types/brainyInterface.js'
 
 /**
  * Default augmentations that ship with Brainy