Update maintained examples for the Ender-60 default

[numerai-hosted-agent-bot]

Summary

• pin every maintained Numerai notebook to explicit v5.3 target_ender_60, including 16-era embargoes, mature-target validation filtering, and a clear warning for pre-cutover/stale dataset caches
• update agent defaults, benchmark references, skills, analysis helpers, tests, and baseline configs for Ender-60 while keeping Ender-20-named configs explicitly pinned
• replace ambiguous cached pickles with Python 3.12, dataset/target-versioned artifacts and committed SHA-256 provenance
• add a reproducible validation/live example-prediction generator and make pull requests execute all maintained Numerai notebook sources

Validation

• Python 3.12.13 end-to-end execution of:
  • numerai/example_model.ipynb
  • numerai/hello_numerai.ipynb
  • numerai/feature_neutralization.ipynb
  • numerai/target_ensemble.ipynb
• loaded every regenerated pickle under Python 3.12 and generated finite, index-aligned live predictions
• PYTHONPATH=numerai python -m unittest numerai.agents.tests.test_target_transforms -v
• python -m compileall -q numerai/agents numerai/generate_example_predictions.py
• notebook JSON/code-cell compilation, workflow YAML parsing, provenance hash verification, and git diff --check

Generated Data-team handoff candidates:

• validation: 4,107,040 rows, SHA-256 9587b14138c572fd041c1a7c05f0b36a53a3991f911aca162eae8bae9f82a2b3
• live: 7,034 rows, SHA-256 89b4702157b68bee4bfedd0e21e0b7368274c4f7fc861ccbe0af2853a8d7cb45
• exact model/notebook provenance: cached-pickles/v53_ender60_provenance.json

No GitHub check was attached to this PR because the pull_request trigger is introduced by this PR; an attempted manual workflow dispatch returned GitHub HTTP 500. The equivalent workflow steps were run locally under its pinned Python 3.12 dependency set.

Coordination

• Linear: T-594
• Tournament docs/website/integration PR: https://github.com/numerai/monorepo-tournament/pull/1141
• Data publication remains outside this PR; the prediction candidates and committed provenance are the handoff evidence.