[TypeDeclarationDocblocks] Return empty "[]" as "mixed[]" instead of "array{}" on bare "@return array"

[TomasVotruba]

When a method has a bare @return array docblock and its sole body statement is return [];, DocblockReturnArrayFromDirectArrayInstanceRector previously rewrote it to @return array{}.

array{} describes an always-empty array shape, which is rarely the intent for a method that just happens to return [] in one branch. This turns that case into the looser, more useful mixed[]:

 /**
- * @return array
+ * @return mixed[]
  */
 public function getRefreshTokenKeys()
 {
     return [];
 }

Scope kept narrow on purpose:

• only fires on a bare @return array tag (not @return mixed, iterable, or an existing generic),
• only for a direct empty return [],
• @return mixed[] and typed X[] empties keep being skipped, and no-docblock empties keep generalizing as before.

https://claude.ai/code/session_011MyFdoaYnfDEvdM9o3kiyq