Compact: add canonical composition-safe family surfaces

[yshyn-iohk]

Closes #490

Parent: #487
Stack parent: #508

Summary

• establish @midnight-ntwrk/credential-compact as the executable canonical Compact VC/VP owner and equivalence-test the retained private facade
• add thin standalone and dependency-free, family-prefixed composable entrypoints for birth and hello-family
• add a deterministic, explicitly non-authoritative two-family Compact fixture plus package/clean-consumer coverage
• regenerate only governed family and transitive managed consumers and update the public fixture manifest

Scope and context

This Stage 1 child provides public standalone/composition surfaces and collision evidence. It is stacked on codex/issue-489-profile-boundaries. Birth and hello-family declare canonical-core dependency edges so Turbo invalidates generated artifacts when the core changes.

Acceptance criteria

• One canonical Compact VC/VP core; retained shared facade files are equivalence- and mutation-tested
• Core, birth, and hello standalone entrypoints compile independently
• Birth and hello compile together with the shared core included once and family-prefixed symbols
• The two-family fixture is labeled non-authoritative composition evidence
• Governed Compact fixture inventory validates after deterministic regeneration

Definition of done

• Focused lint and core/birth/hello package tests pass
• Actual Compact 0.31.1 standalone and two-family compiles pass
• Composition, artifact/catalog, package-boundary, release, docs, and build-cone checks pass
• ./run.sh --light passes after review-driven fixes
• Required external Codex review ran once; both actionable findings were fixed
• Current-head CI is probed after draft PR creation

Artifact evidence

• birth circuits: 105 → 74; proof circuits 0 → 0; k N/A
• hello circuits: 90 → 59; proof circuits 0 → 0; k N/A
• two-family fixture: 86 circuits, 0 proof circuits, k N/A
• transitive age-gate demo and hello-verifier compiler/JS deltas are governed regeneration consequences; proof artifacts are unchanged

Non-goals

No aggregate multi-credential authority, profile resolver, protocol/application orchestration, status/trust/time semantics, deployable business circuit, family graduation, or production-assurance claim.