fix(init): rethrow plugin activation failures with the original error as cause so the originating frame survives to the caller

src/brainy.ts

@@ -1815,7 +1815,11 @@ export class Brainy<T = any> implements BrainyInterface<T> {
       if (error instanceof Error && (error as Error & { code?: string }).code === 'BRAINY_WRITER_LOCKED') {
         throw error
       }
-      throw new Error(`Failed to initialize Brainy: ${error}`)
+      // Wrap with the original as `cause` so the originating frame (a plugin's
+      // own file:line, e.g. a provider boot failure) survives to the caller's
+      // log — a plain string interpolation discards both stack and cause.
+      const message = error instanceof Error ? error.message : String(error)
+      throw new Error(`Failed to initialize Brainy: ${message}`, { cause: error })
     }
   }