feat(variation): add bounded ensemble chunk lifecycle

[d-sorgcodexagent]

Summary

• add an immutable, resource-bounded in-process complete-ensemble header/chunk/sink lifecycle
• bind every provisional row to exact sampled-input, frame, trace, validity, and impact-time authority
• preserve the public materialized API and per-trial progress through a compatibility collector
• abort without committed authority on cancellation or executor/sink failures

Verification

• 55/55 focused lifecycle, domain, and adapter tests
• 330/330 broader Rate/shared-variation tests
• Python 3.12 + NumPy 2.3.5 + Mypy 1.13 exact hosted combination
• Ruff check and format
• docs governance, changed-Python policy, assertion policy, module-size budget, diff hygiene
• two independent adversarial reviews: GO on exact commit 11a6991

Scope and remaining work

This is an R11.5 foundation, not R11.5 completion. The compatibility collector still materializes the final trace tensor; request samples/configs remain eager. Durable chunk transport, resume/checksum semantics, a non-materializing production sink, complete event/state/torque authority, and measured peak-memory evidence remain open.

Stacked on #4405. Preserve ordinary protected dependency order.