Promote placeholder services and workflows into minimal operational slices

[justinrayshort]

Summary

Promote metadata-only placeholder service and workflow crates into minimal operational slices so deployable workspace members represent real governed behavior rather than boundary declarations only.

Primary Architectural Plane

services / workflows / shared

Owning Subsystem

services/security-service, services/audit-service, services/identity-service, workflows/access_review, touched adjacent governance helpers

Architectural References

• ARCHITECTURE.md
• docs/architecture/layer-boundaries.md
• docs/architecture/runtime-composition.md

Integration Boundaries

Allowed touchpoints: targeted placeholder services and workflows, touched shared policy or identity helpers, and integration tests.
Explicit non-goals: deep domain expansion beyond minimal operational slices.

Scope In

• Add typed request or response models and a minimal executable entry path for each targeted placeholder crate
• Add boundary and integration tests demonstrating governed interaction across service and workflow edges
• Start with highest-governance slices around security, identity-adjacent review, and audit assurance
• Open follow-up consolidation issues when a remaining placeholder still cannot justify a runtime slice

Scope Out

• Broad domain modeling beyond the minimal operational slice for each targeted crate
• UI or infrastructure changes

Acceptance Criteria

• Each targeted placeholder crate exposes at least one real behavior path with tests
• Integration tests prove the promoted slice works through governed contracts rather than direct private coupling
• Full repository validation remains green

Validation Requirements

• cargo fmt --all --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo test --workspace --all-targets
• cargo xtask architecture audit-boundaries

Rollback Considerations

Revert each promoted slice as a unit so targeted services and workflows either remain fully operational or cleanly return to metadata-only state.

Parent Issue

• Core runtime hardening and service promotion program #111