Consume Prophet Trust Chain evidence in action admission

[mdheller]

Context

SocioProphet/prophet-platform now carries docs/standards/PROPHET_TRUST_CHAIN_V0.md plus the first contracts/trust-chain/admit-artifact-* fixtures and validator.

Guardrail Fabric owns deterministic runtime enforcement and claim/action admission for models, agents, tools, RAG packages, knowledge bases, and runtime deployments. This issue implements the Guardrail slice of Prophet Trust Chain.

Target

Add action-admission examples and validation coverage that consume Prophet Trust Chain evidence before effectful action.

The first supported artifact path should be:

RuntimeAsset evidence
  -> package/runtime posture
  -> policy profile
  -> guardrail decision
  -> allow, deny, escalate, quarantine, allow_with_context, or provisional

Acceptance criteria

• Add fixtures or examples for allowed and denied RuntimeAsset admission decisions.
• Deny or quarantine when required trust-chain evidence is missing for regulated-enterprise production use.
• Preserve fail-closed behavior for absent policy, stale evidence, or blocked package/runtime posture.
• Decision artifacts remain compatible with sourceos.guardrail.decision.v0.1 or document the extension boundary.
• Docs reference SocioProphet/prophet-platform/docs/standards/PROPHET_TRUST_CHAIN_V0.md and the platform trust-chain fixtures.

Non-goals

• Do not implement scanner integrations.
• Do not treat package scan output alone as admitted truth.
• Do not mutate infrastructure directly in this tranche.

[mdheller]

Implementation pass landed for the Prophet Trust Chain runtime/action-admission slice.

Commits:

• 92e5655b25ad2f719581bd5a2655556fc02f0377 — added allow fixture: examples/trust-chain/runtime-asset-admission.allow.json.
• 412146a72e7d36ff0101977d96e64210f9ca3a83 — added deny fixture: examples/trust-chain/runtime-asset-admission.deny.json.
• 73c0dff0d0e5baffa0e92847b106d812e89e0b78 — added tools/validate_trust_chain_runtime_admission.py.
• 2c8e5ae782fce7d4e69ca36a73025eee07d24705 — wired Trust Chain runtime-admission validation into tests/test_schema.py.
• 191e582e4f4f5e7b004bb79386f08179abfc2778 — documented the Trust Chain runtime-admission lane in the README.

Implemented acceptance coverage:

• Fixtures remain compatible with sourceos.guardrail.decision.v0.1.
• Allow fixture consumes RuntimeAsset Trust Chain evidence and permits agent continuation.
• Deny fixture records missing/blocked production evidence, stops agent continuation, and requires human approval.
• Validator checks:
  • policyId = trust-chain/runtime-asset-admission
  • evidence.actionClass = runtime
  • artifactType = RuntimeAsset
  • required refs on allow: SBOM, VEX, lockfile, signature, scan, policy profile, and admission decision
  • strict allow posture: no known blocking findings, current-for-scope patch posture, trusted source channel
  • strict deny posture: known blocking findings, patch required, production denied
  • action effects: allow permits continuation; deny stops continuation and requires human approval
• Tests call the validator and inspect allow/deny fixture effects.
• README links back to the Prophet Platform standard, admission contract, and implementation map.

Boundary preserved: Guardrail Fabric enforces runtime/action admission decisions and records compatible decision artifacts. It does not perform live scanning, certify runtime production readiness by itself, mutate infrastructure directly, or replace Lattice Forge, Policy Fabric, AgentPlane, Model Governance Ledger, or Prophet Platform admission authority.

Status: functionally complete pending CI validation and review changes.