DONE: Deduplicate exact replay-planner path validation within one stable-checkout invocation

[JoyboyBrian]

DONE — PR6087, exact head f4f73e14604fa8f738ae3e5caa2381551e20ec0d.

["Five-line production change eliminates duplicate declared-input validation within each stable-checkout plan.", "Existing validation error behavior and complete consumer/cause/hash output retained.", "All 40 benchmark results match the baseline by complete structured equality."]

Scoped proof/code review and the relevant local verification are complete; exact evidence, reproduction and remaining obligations are in the PR. New commits and public contribution use JoyboyBrian. Hosted CI is separate and must be read at this head. No selected-frontier change, merge or human/formal-kernel acceptance is claimed. Prepared with substantial OpenAI Codex assistance; predecessor attribution retained. No further work reserved by this claim.

{
  "schema": "integer-mult-coordination/v1",
  "kind": "DONE",
  "task": "replay-runtime",
  "scope": "Deduplicate exact replay-planner path validation within one stable-checkout invocation",
  "base": "721c03822c421b7f7fcbb2598993b947c4d88419",
  "expiry": null,
  "artifact": "https://github.com/CrocSwap/integer-mult-bounds/pull/6087"
}