Preserve parent-local and reducer outcome precedence

[alexlopashev]

Closes #151

Outcome

• combine the exact retained reducer result with parent-local obligation dispositions under the generic Refuted > Faulted > Unresolved > Satisfied precedence
• preserve a decisive reducer refutation when an independent parent-local obligation is unresolved
• reject a weaker satisfied reducer result when a parent-local obligation remains unresolved
• keep child-discharge labels behavior-neutral
• align SEMANTICS, README, threat-model, and KRN-08 conformance claims

Red-to-green evidence

Base: 5e29b2c874cba460249010b791f617dd0028d8e8

Before the implementation change, the focused regression decisive_refutation_outweighs_an_unresolved_parent_obligation failed with BHCP7302 claimed execution outcome does not match checked parent obligation dispositions.

After the implementation change:

• mise exec -- cargo test --test proof_checker: 24 passed
• complementary regression unresolved_parent_obligation_rejects_a_weaker_satisfied_reducer_result confirms the checker still rejects a weaker satisfied result with BHCP7302
• affected profile, CI, schema, graph, verification, and policy-evidence targets passed
• mise exec -- cargo clippy --all-targets -- -D warnings passed
• git diff --check passed

Full validation

The unchanged canonical gate passed from a clean, explicitly bounded experiment-controller scratch directory:

mise exec -- cargo fmt --check
mise exec -- cargo clippy --all-targets -- -D warnings
mise exec -- cargo test --all-targets
mise exec -- cargo build --release
mise exec -- cargo test --test schema_fixtures

Documentation impact

Updated SEMANTICS.md, README.md, THREAT_MODEL.md, and conformance/v0/README.md to publish the same behavior-neutral precedence boundary.

Residual risk

This slice checks proof outcomes at the obligation-graph boundary. Execution-graph construction, runtime enforcement, and final evidence-graph assembly remain separately deferred as already documented.

Exact reviewed head

8eac3b865cd57b0dd514881685a6a2190922a37c

[alexlopashev]

Independent review evidence from Codex task /root/review_151 (distinct from authoring task /root; shared GitHub account, so this is not represented as a formal GitHub approval).

Reviewed exact immutable head 8eac3b865cd57b0dd514881685a6a2190922a37c against issue #151, the surrounding SEMANTICS.md proof contract, generic checker implementation, obligation-status aggregation, and proof regressions. No actionable findings.

The change preserves the exact retained reducer as child-composition authority, applies only the generic Refuted > Faulted > Unresolved > Satisfied ordering when reconciling parent-local dispositions, rejects weaker incompatible reducer outcomes, and introduces no reducer-, quantifier-, behavior-, or child-discharge-label-specific proof rule.

Independent validation at the reviewed head:

• mise exec -- cargo test --test proof_checker: 24 passed
• mise exec -- cargo clippy --all-targets -- -D warnings: passed
• git diff --check 5e29b2c874cba460249010b791f617dd0028d8e8..8eac3b865cd57b0dd514881685a6a2190922a37c: passed

Merge remains gated on all required remote checks and an unchanged head SHA.