Add history-aware self-hosting search

[Darreckk]

What changed

• adds controller-directed island allocation with quality bands, diversity and token-efficiency accounting
• persists complete measured artifact history across displacement, rejection, migration and checkpoint resume
• exposes bounded archive context and evaluator-defined proposal neighborhoods to generation
• records provider receipts, rejected proposals, model usage and measured/archive outcomes separately
• makes program and phenotype identity artifacts configurable and fixes selection-metric reporting
• adds focused regression coverage for checkpoint continuation, scheduling, migration, identity and parallel proposal handling

Why

Long-running self-hosting searches were forgetting previously measured structures once they left the live population, allowing rediscovery and weakening controller decisions. These changes make the complete measured history durable and auditable while keeping prompts bounded.

Validation

• pytest -q tests --ignore=tests/integration: 476 passed, 53 subtests passed
• isolated sdist and wheel build succeeded
• twine check passed for both artifacts
• exercised in a 53-call, four-worker TheoryFoundry campaign with checkpointing, migration, early stopping and 54 independent final confirmations

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