feat(complexity): add fixed-clock deterministic promise completions - #1991

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

`Turing.MultiTapePTM.SolvesPromiseWithBoundedErrorInTime` and `Turing.MultiTapePTM.DecidesWithBoundedErrorInTime` (Complexity/Computability/Complexity/Classes/Time.lean:107) share a 435-node subterm, 71% of the smaller body, built from `Turing.MultiTapeMachine.Config`, `Empty`, `Function.Embedding`, `PMF.support`, `Cslib.ProbComp.eval`, `Turing.MultiTapePTM.runClosedConfigFrom`. Advisory only; see the job summary.

`Turing.MultiTapePTM.SolvesPromiseWithBoundedErrorInTime` and `Turing.MultiTapePTM.DecidesByMajorityInTime` (Complexity/Computability/Complexity/Classes/PP/Time.lean:88) share a 435-node subterm, 70% of the smaller body, built from `Turing.MultiTapeMachine.Config`, `Empty`, `Function.Embedding`, `PMF.support`, `Cslib.ProbComp.eval`, `Turing.MultiTapePTM.runClosedConfigFrom`. Advisory only; see the job summary.