Draft: Optimize late-horizon economy history processing

[KevinBigham]

Outcome

This draft preserves the active Goal 32 / roadmap-item-18 work on GitHub without landing it on main.

The branch contains the four semantics-neutral late-horizon performance seams and their focused tests. Production source is frozen at 5a4eb60f8b1890803117a84a613d43af605f47dc and has an independent source-review verdict of P0/P1/P2 0/0/0.

Current gate

• Prior custom and one-file proof candidates stopped before timing and remain historical evidence.
• Their temporary-only dirty checkouts and checkpoint files were removed externally; committed revisions and recorded reviews survive.
• Kevin's standing authority opens one fresh persistent proof route: frozen-lockfile dependency preparation, one corrected proof-only test candidate, static Sol 0/0/0, then one fresh import probe.
• The R/P/H diagnostic and final admission are still unspent.
• The unchanged final adjusted cap remains 2,040,000ms; the process timeout remains 2,400,000ms.
• Item 19 remains closed.

Verification represented here

• Frozen source focused tests: sim-core 64 passed; web 225 passed.
• Direct sim-core/web typechecks and root typecheck passed on the source freeze.
• All four deliberate structural mutants failed at their intended guards and were restored.
• Independent frozen-source review: MERGE_READY, P0/P1/P2 0/0/0.
• Documentation/authority sweep review: MERGE_READY, P0/P1/P2 0/0/0; exact diff SHA-256 04bd3967ffdbe18821c1ae1d43ba8a51ffaa9d6a4ec72657b6fd0e293011794d.

This PR must remain draft until the fresh proof route, no-retry diagnostic, conditional final admission, full repository gates, and final adversarial review all pass. It must not be deployed or released as Goal-32-complete in its current state.