feat: add VPCT benchmark task

[Luodian]

Summary

• Add a new auto-discovered vpct benchmark task under lmms_eval/tasks/vpct/.
• Implement VPCT prompt + image loading + answer parsing with vpct_accuracy and vpct_answered_rate metrics.
• Load public VPCT assets from camelCase12/vpct-1 with token: false/token=False to avoid expired local HF token issues.

Validation

• HF_TOKEN= uv run python -m lmms_eval --model dummy_video_reader --model_args \"response=answer(2)\" --tasks vpct --limit 8 --batch_size 1 --log_samples --output_path ./outputs/vpct_smoke
• Score table from smoke run:
  • vpct_accuracy: 0.375
  • vpct_answered_rate: 1.000
• JSONL sample log: outputs/vpct_smoke/20260222_225543_samples_vpct.jsonl
  • Verified non-empty model outputs, e.g. filtered_resps: \"answer(2)\".

Smoke Validation (limit=8)

Status: PASS (LMM-299 / vpct)

Output Table

Metric	Value
vpct_accuracy	0.125
vpct_answered_rate	0.750

Sample Output

Sample 1 (doc_id: 0)

• Input: You are an expert physics simulator. Looking at this image of a ball-and-bucket simulation, predict which bucket (numbered 1, 2, or 3 from left to right) the ball will eventually fall into. ↵ Respond with answer(X), where X is 1, 2, or 3.
• Model Output: This is a classic physics simulation problem, often related to projectile motion or, in this simplified 2D representation, the trajectory of a falling object influenced by gravity
• Reference: 3
• Scores: N/A
• Tokens: output=31, reasoning=0

Sample 2 (doc_id: 1)

• Input: You are an expert physics simulator. Looking at this image of a ball-and-bucket simulation, predict which bucket (numbered 1, 2, or 3 from left to right) the ball will eventually fall into. ↵ Respond with answer(X), where X is 1, 2, or 3.
• Model Output: This is a classic physics simulation problem, often related to projectile motion or, in this simplified 2D representation, the trajectory of a falling object under gravity.
• Reference: 1
• Scores: N/A
• Tokens: output=31, reasoning=0

Test Params

uv run python -m lmms_eval --model openai --model_args "model_version=google/gemini-2.5-flash-lite-preview-09-2025" --tasks vpct --batch_size 1 --limit 8 --log_samples