[gmemmy]

Problem

Single-platform evidence packs could retain cross-platform comparison states, include artifacts from an undeclared platform, or pass through the legacy two-platform helper with an incoherent scope. That could make an iOS-only or Android-only run appear broader than the evidence actually supports.

What changed

• Reject present platforms, proofs, attempts, evidence, and verdicts outside the declared platform scope.
• Require single-platform packs to use comparisonStatus: not_available.
• Keep the legacy two-platform helper strict: coherent Android+iOS input is supported; incoherent input is rejected or returned as not evaluable as appropriate.
• Add focused schema, assembler, publication-summary, and packed-package coverage.
• Document the runtime semantic checks that cannot be expressed as sibling-array relationships in JSON Schema.

Why this approach

Platform scope is part of the evidence claim, not presentation metadata. The assembler and runtime validator therefore enforce cross-record relationships, while the schema enforces the parts it can represent directly.

Proof

• pnpm typecheck - passed.
• Focused CI evidence tests - 144/144 passed.
• pnpm release:check - passed on the exact reviewed content under an isolated resource lease.
• Full repository tests - 1,884/1,884 passed.
• Packed package smoke - passed.
• Installed-consumer rehearsal - passed.
• Independent exact-diff review - clean, with no P0-P3 findings.
• Device and live runtime proof - not run; this PR changes package validation and evidence-contract behavior.

Risks and limits

• Existing single-platform artifacts that incorrectly declare a comparable cross-platform state will now fail validation.
• JSON Schema cannot express every relationship between sibling platform arrays; ASL's runtime validator remains authoritative for those checks.
• This does not add a provider, capture a device, or prove product behavior.

Stack/review order

• Base: fix(evidence): preserve package version compatibility #349.
• Review after fix(evidence): preserve package version compatibility #349 and merge after it.
• This is the final platform-scope integrity correction in the current evidence-contract stack.

Follow-ups

• Complete cumulative review of the remaining publication and CLI surfaces before preparing the next immutable package candidate.