Route models only through Prophet Trust Chain admitted runtime and provider evidence

[mdheller]

Context

SocioProphet/prophet-platform now carries docs/standards/PROPHET_TRUST_CHAIN_V0.md and the first trust-chain admission fixtures.

Model Router owns governed model and provider routing under policy. This issue implements the Model Router slice of Prophet Trust Chain.

Target

Bind routing decisions to model factsheets, provider posture, cost limits, fallback policy, and runtime/provider admission evidence.

The first path should cover:

ModelRouteDecision
  -> requested model capability
  -> model factsheet/eval refs
  -> runtime or hosted-provider posture refs
  -> policy profile refs
  -> trust-chain admission refs
  -> cost and fallback posture
  -> allow, downgrade, fallback, deny, or review decision

Acceptance criteria

• Add schema/example fields linking route decisions to trust-chain admission refs.
• Add a valid route example where a local model route is allowed because model and runtime evidence are present.
• Add a fallback/downgrade example where a route changes because a preferred model, provider, or runtime lacks admission evidence.
• Add a denied example for regulated-enterprise production use with missing model/runtime/provider evidence.
• Validator or tests cover the examples.
• Docs reference SocioProphet/prophet-platform/docs/standards/PROPHET_TRUST_CHAIN_V0.md.

Non-goals

• Do not call live providers in this tranche.
• Do not store provider credentials.
• Do not treat model availability as authorization.

[mdheller]

Implementation pass landed for the Prophet Trust Chain model-route decision slice.

Commits:

• 2b327b2ba42c20160dfe812225d1b639e9c3c82d — added schemas/trust-chain-model-route-decision.v0.1.schema.json.
• b059f1d773663db26917a50c904e94d259229e42 — added allowed local route fixture.
• 342271f88fede52651f3b752f847c2b175823906 — added fallback route fixture.
• e6c6c0ae59a28db2f2d0bda3ff7940fe6e7f7fc8 — added denied route fixture.
• d9cef64d136a45f6b910acfc45f2cf90fbfd3d27 — added tools/validate_trust_chain_model_route_decision.py.
• d6e0b72dfb7db5c32e38ae45dbd0264a8510ad03 — added pytest coverage in tools/tests/test_trust_chain_model_route_decision.py.
• 2a05593eff3cb639f2dae70004444760256aa2ab — wired validate-trust-chain-model-route-decision into the Makefile validation path.
• c985a962f29ecb2d36d90b27dc967838a2ebf859 — documented the Trust Chain model route-decision lane in the README.

Implemented acceptance coverage:

• Machine-readable Trust Chain model route-decision schema exists.
• Allow fixture routes to an admitted local model/runtime with model factsheet, eval receipt, runtime admission, policy profile, and Guardrail evidence present.
• Allow fixture denies provider call and prompt egress even while allowing the local route.
• Fallback fixture rejects a preferred hosted/provider route because provider admission evidence is missing, then falls back to the admitted local route.
• Deny fixture selects no route when no candidate has complete Trust Chain evidence.
• Validator enforces selected allow/fallback routes carry all required Trust Chain refs.
• Validator enforces fallback is justified by incomplete preferred-route evidence.
• Validator enforces deny has no selected route, requires human review, and carries remediation authority.
• Makefile validation path now includes validate-trust-chain-model-route-decision.
• README links back to the Prophet Platform standard, admission contract, and implementation map.

Boundary preserved: Model Router selects routes under policy and evidence constraints. It does not call live providers, store provider credentials, treat model availability as authorization, replace Model Governance Ledger model promotion evidence, replace Lattice Forge runtime evidence, replace Policy Fabric policy profiles, replace Guardrail Fabric action admission, replace AgentPlane execution evidence, or replace Prophet Platform admission composition.

Status: functionally complete pending CI validation and review changes.