Define decision monoids

[nilp0inter]

Summary

• Add explicit public decision monoids for composite terminal resolution.
• Keep AnyOf as disjunction: ACCEPT_H0 < INCONCLUSIVE < ACCEPT_H1.
• Correct AllOf default resolution to conjunction: ACCEPT_H1 < INCONCLUSIVE < ACCEPT_H0.
• Preserve composite child evidence with terminal_results on CompositeResult.
• Make n_decided count actual terminal direct children, including AnyOf early-stop cases where n_decided may be less than n_total.
• Add Hypothesis monoid-law tests and update composite property-test oracles.
• Add direct evidence-preservation tests for AllOf, AnyOf, and nested composites.
• Document monoid semantics and CompositeResult evidence semantics in Sphinx docs/API reference.

Verification

• nix develop --command task lint
• nix develop --command task typecheck
• nix develop --command task docs
• nix develop --command task test

Notes

• Custom resolve= behavior is unchanged.
• This fixes the previous AllOf default resolver bug where AllOf used the AnyOf-like resolver.
• The scalar composite decision is still a policy-level projection; child-level terminal evidence is now preserved in CompositeResult.terminal_results.