integrations/art_framework: add ART↔verifiers adapter

[Occupying-Mars]

Description

Adds ART ↔ verifiers integration under integrations/art_framework:

• art_framework.py: loads ART task configs, converts tools to ToolEnv, exact-match rubric by default, optional JudgeRubric.
• utils/art_adapter.py: ART→verifiers tool conversion with strict JSON schemas (no additionalProperties).
• utils/verifiers_adapter.py: verifiers→ART export (schema-only).
• examples/calculator.json: small, real, runnable example.
• test_env.py: unit test for conversion, parser, and reward.

Key behaviors:

• Enforces strict JSON tool schemas compatible with agents’ validator.
• ARTParser extracts the final answer from the configured completion tool.
• Works as an integration (installed via vf-install, not a core env).

Type of Change

• [x] New feature (non-breaking change which adds functionality)
• [x] Documentation update
• [x] Test improvement

Testing

• [x] All existing tests pass when running uv run pytest locally.
• [x] New tests have been added to cover the changes

What I ran:

• Unit test (no network):
  • uv run pytest integrations/art_framework/test_env.py -q
• Local install + eval (exact-match rubric):
  • uv run vf-install art_framework -p integrations
  • UV_NO_PROJECT=1 uv run vf-eval -s art_framework -a '{"task_config_path":"integrations/art_framework/examples/calculator.json"}' -m gpt-5-nano -n 2 -r 1
• Optional judge (requires OPENAI_API_KEY):
  • export OPENAI_API_KEY=sk-...
  • UV_NO_PROJECT=1 uv run vf-eval -s art_framework -a '{"task_config_path":"integrations/art_framework/examples/calculator.json","use_llm_judge":true,"judge_model":"gpt-5-nano"}' -m gpt-5-nano -n 2 -r 1

i tested it myself since it's just integration didn't really need to see rollouts but it works

Checklist

• [x] My code follows the style guidelines of this project as outlined in AGENTS.md
  • ruff clean; explicit types where useful; fail-fast error handling
• [x] I have performed a self-review of my own code
• [x] I have commented code where non-obvious (conversion, strict schema rationale)
• [x] I have made corresponding changes to the documentation
  • integrations/art_framework/README.md with Overview, Quickstart, Env Args, ART config format, Portability
• [x] My changes generate no new warnings
• [x] Any dependent changes have been merged and published
  • None; integration is self-contained and optional

Additional Notes

• Alignment: Follows integrations layout and roadmap; mirrors patterns from MCP and wiki_search (ToolEnv + optional JudgeRubric).
• Strict schema: Tools are generated with explicit parameters (no **kwargs) to satisfy agents’ strict JSON schema validation (no additionalProperties).
• Portability: Includes export helper and runnable example config.
• Known limitations: Example implementation supports simple lambdas for demos; real deployments should provide proper functions/modules.

[CLAassistant]

All committers have signed the CLA.

[Occupying-Mars]

@willccbb (sorry for the tag again just looking for a review)