fix(32b): use main branch for workdir instead of feat/vl-multimodal-support

[dzorlu]

Summary

• Fix workdir ref in openenv-fleet-grpo-qwen3-32b.yaml to use main instead of feat/vl-multimodal-support
• The old branch had an outdated prepare_dataset.py that doesn't support comma-separated env_keys

Problem

When running the 32B training workflow with ENV_KEYS=reddit,zillow,forums-homes,..., the job fails with:

FileNotFoundError: Unable to find '/root/data/fleet/tool_use/train.parquet'

Root cause: The feat/vl-multimodal-support branch has the OLD prepare_dataset.py that does exact string matching:

# OLD (feat/vl-multimodal-support)
if env_filter:
    tasks = [t for t in tasks if t.get("env_key") == env_filter]  # exact match

While main has the FIXED version that supports comma-separated values:

# NEW (main)
if env_filter:
    env_list = [e.strip() for e in env_filter.split(",") if e.strip()]
    tasks = [t for t in tasks if t.get("env_key") in env_list]  # list membership

Test plan

• Re-run the training workflow with the same ENV_KEYS and verify dataset is created correctly

🤖 Generated with Claude Code