PR 06: Add builtin sample environments

[cm2435]

Review Guide

Stack position: PR 06, base codex/episode-sample-pr05-submit-materialize, head codex/episode-sample-pr06-builtin-environments.

Implements RFC Docs

• 04-ecosystem/02-builtins.md: builtin environment classes, loading, row-to-sample conversion, row-dependent components.
• 02-core-authoring-api.md: concrete Environment -> Sample -> Task examples.
• 09-implementation-plan/07-pr-06-builtin-environments.md.

Why This PR Exists

The new public API needs real builtin environments, not just abstract examples. This PR ports the builtin benchmark domains into environment classes that own row loading and sample construction.

What Actually Changes

• Adds builtin environment classes under ergon_builtins/environments:
  • MiniF2FEnvironment
  • SweBenchVerifiedEnvironment
  • ResearchRubricsEnvironment
  • GDPEvalEnvironment
• Each environment owns loading plus _sample_from_row(...) and produces Sample.from_tasks(...) with existing task classes.
• Adds shared row-dependent resolution in _resolve.py so worker/evaluator/sandbox values can be objects or row callables.
• Adds SWE streaming support.
• Keeps MiniF2F, ResearchRubrics, and GDPEval materialized-only.
• Existing benchmark modules remain as compatibility wrappers that delegate build_instances() through environment all_samples().

Gotchas / Review Risks

• Old Benchmark classes are still present as shims. This PR ports behavior but does not delete compatibility wrappers.
• Default loaders can hit external/Hugging Face data; tests use fake loaders to keep unit coverage deterministic.
• SWE streaming rejects all_samples(); the other environments are materialized-only.
• loader: Any | None is intentionally flexible but weakly typed.
• ResearchRubrics has special handling for empty rubric criteria from row payloads.

Cleaned Later

• Builtin benchmark wrappers and old benchmark-facing docs are removed/rewired later.
• Examples are updated in PR 07.
• CLI/read/dashboard consumption lands after the builtins exist.

Validation Notes

Review the environment unit tests under ergon_builtins/tests/unit/environments, especially row-dependent worker/evaluator/sandbox resolution, SWE streaming behavior, and compatibility wrapper coverage.

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E2E smoke — minif2f

No PNG screenshots were uploaded for this leg. See screenshots/pr-125 for the uploaded placeholder.

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E2E smoke — swebench-verified

No PNG screenshots were uploaded for this leg. See screenshots/pr-125 for the uploaded placeholder.

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E2E smoke — researchrubrics

No PNG screenshots were uploaded for this leg. See screenshots/pr-125 for the uploaded placeholder.

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E2E smoke — swebench-verified

Screenshots pushed to screenshots/pr-125.

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Screenshots pushed to screenshots/pr-125.

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Screenshots pushed to screenshots/pr-125.

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Screenshots pushed to screenshots/pr-125.

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Screenshots pushed to screenshots/pr-125.

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Screenshots pushed to screenshots/pr-125.

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Screenshots pushed to screenshots/pr-125.

[github-actions]

E2E smoke — researchrubrics

Screenshots pushed to screenshots/pr-125.

[github-actions]

E2E smoke — minif2f

No PNG screenshots were uploaded for this leg. See screenshots/pr-125 for the uploaded placeholder.

[github-actions]

E2E smoke — swebench-verified

No PNG screenshots were uploaded for this leg. See screenshots/pr-125 for the uploaded placeholder.

[github-actions]

E2E smoke — researchrubrics

No PNG screenshots were uploaded for this leg. See screenshots/pr-125 for the uploaded placeholder.

[github-actions]

E2E smoke — researchrubrics

No PNG screenshots were uploaded for this leg. See screenshots/pr-125 for the uploaded placeholder.

[github-actions]

E2E smoke — swebench-verified

No PNG screenshots were uploaded for this leg. See screenshots/pr-125 for the uploaded placeholder.

[github-actions]

E2E smoke — minif2f

No PNG screenshots were uploaded for this leg. See screenshots/pr-125 for the uploaded placeholder.

[github-actions]

E2E smoke — researchrubrics

No PNG screenshots were uploaded for this leg. See screenshots/pr-125 for the uploaded placeholder.

[github-actions]

E2E smoke — minif2f

No PNG screenshots were uploaded for this leg. See screenshots/pr-125 for the uploaded placeholder.

[github-actions]

E2E smoke — swebench-verified

No PNG screenshots were uploaded for this leg. See screenshots/pr-125 for the uploaded placeholder.

[cm2435]

Closed after landing the cumulative episode/sample stack snapshot through PR132 directly onto dev in merge commit 1c22130. This PR's changes are included in dev.