* Keep pad-named pad_tokens; defer pad repair to shared unsloth_zoo.pad_token
A pad-named token (e.g. <|vision_pad|>) is a valid pad. The narrow fallback that
stripped vision pad tokens on text-only models is now a no-op; the active path
delegates to the shared fix_pad_token in unsloth_zoo, which keeps pad-named tokens
and only heals missing / eos-collision / out-of-range pads.
This fixes the Qwen3-4B-Base load crash (its config ships pad_token=<|vision_pad|>):
the old swap could not find a safe text pad (eos is <|endoftext|>, no unk_token) and
left the tokenizer broken. Removes the unused _VISION_PAD_TOKENS / _SAFE_TEXT_PAD_TOKENS
sets. Tests updated.
Pairs with unslothai/unsloth-zoo#831.
* Remove _fix_vision_pad_token; inline the no-op fallback
A pad-named token (e.g. <|vision_pad|>) is a valid pad, so the old vision-pad swap
helper has no purpose. _fix_pad_token now returns the tokenizer unchanged when the
shared unsloth_zoo.pad_token module is unavailable, instead of routing through a
no-op helper. Test WANTED set updated.
4929c5f769