refactor(cdsl_engine): sink atomic runtime capability flags into schema contracts

Phase 4 of the decoupling refactor (behavior-preserving):
- profile_schema.json: every operation contract now carries
  runtime_capability {body_mutating, requires_active_body,
  replayable, requires_selector, open_profile_ok} (single source of truth)
- operation_contracts.py: validates and forwards the flags
- capabilities.py: the five data-classification frozensets are now
  derived from the schema at import time; dispatch-logic sets
  (_HOLE_ATOMICS, _PATTERN_ATOMICS, extent constants) stay in code
- test_profile_schema.py: completeness + structural invariants test

Equivalence proven by flag counts (27/13/25/6/2) matching the previous
hand-written sets and by the unchanged test-baseline failure set.

backend/engine/cdsl_engine/operation_contracts.py

@@ -31,6 +31,7 @@ def materialized_feature_contracts(profile: dict[str, Any]) -> dict[str, dict[st
         params_schema = raw.get("author_params_schema")
         injected_paths = raw.get("server_injected_paths")
         selector_policy = raw.get("selector_policy")
+        runtime_capability = raw.get("runtime_capability")
         if (
             not isinstance(shape, dict)
             or not isinstance(params_schema, dict)
@@ -38,6 +39,13 @@ def materialized_feature_contracts(profile: dict[str, Any]) -> dict[str, dict[st
             or not isinstance(selector_policy, dict)
         ):
             raise ValueError(f"operation contract is incomplete for {atomic_id}")
+        if not isinstance(runtime_capability, dict) or not all(
+            isinstance(runtime_capability.get(flag), bool)
+            for flag in (
+                "body_mutating", "requires_active_body", "replayable", "requires_selector", "open_profile_ok",
+            )
+        ):
+            raise ValueError(f"operation runtime_capability is invalid for {atomic_id}")
         properties = params_schema.get("properties")
         required = params_schema.get("required")
         if not isinstance(properties, dict) or not isinstance(required, list):
@@ -59,5 +67,6 @@ def materialized_feature_contracts(profile: dict[str, Any]) -> dict[str, dict[st
             "requires_sketch": shape.get("sketch") == "required",
             "selector_slot": selector_policy.get("slot"),
             "selector_token_kind": selector_policy.get("token_kind"),
+            "runtime_capability": dict(runtime_capability),
         }
     return derived