[TS Calls] Register and execute guarded semantic models

[CaelmBleidd]

Part of #360. Depends on #363.

Goal

Provide a deterministic model registry and execute exact or partial constraint-level models through the unknown-call dispatcher.

Why

The registry is only useful when a selected model can produce symbolic successors and send its unsupported domain to the configured residual fallback. The common contract must not depend on how a model is implemented.

Scope

• Register models explicitly with a stable ID, matcher, supported domain, precision, and implementation kind.
• Keep model matching and execution behind backend-neutral interfaces.
• Implement the constraint-level INTRINSIC backend.
• Reject duplicate or ambiguous matches.
• Allow a run to enable a frozen subset of models and record its fingerprint.
• Support models that produce:
  • guarded normal successors;
  • exceptional successors;
  • state changes and aliases;
  • a residual state for unsupported inputs.
• Send every residual state to the fallback selected by [TS Calls] Define model selection and residual fallback profiles #363.
• Record MODEL_APPLIED and residual decisions through [TS Calls] Record unknown-call decisions #364.
• Migrate one existing partial approximation as an end-to-end intrinsic integration case.
• Keep the catalog intentionally small; model-family expansion is handled separately.

Definition of Done

• Model descriptors separate implementation kind, supported domain, and precision.
• Model selection is deterministic and independent of registration order.
• Exact models leave no residual state.
• Partial models split supported and residual domains correctly.
• Residual states use the fallback selected by the active profile.
• Ambiguous registrations fail with a clear diagnostic.
• The catalog fingerprint includes the enabled models and implementation kinds.
• One intrinsic model exercises the full dispatcher–registry–model–fallback path.
• Focused tests cover exact, partial, exceptional, stateful, and ambiguous cases.
• The change is delivered in a dedicated PR linked to this issue and [Epic][TS Calls] Introduce explicit fallback policies and partial semantic models #360.