feat(infospace): add schema compliance validator (S1.2)

Deterministic validation of EntityMeta against declarative schemas:
section presence/word counts, heading format, domain enum values.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

markitect/infospace/__init__.py

@@ -7,9 +7,35 @@ files and analysing infospace collections.
 
 from .models import EntityMeta
 from .entity_parser import parse_entity_file, parse_entity_directory
+from .schema import (
+    ECONOMIC_ENTITY_SCHEMA,
+    EntitySchema,
+    EnumConstraint,
+    SectionRequirement,
+    SectionRule,
+)
+from .validator import (
+    BatchComplianceResult,
+    ComplianceDiagnostic,
+    ComplianceResult,
+    validate_entities,
+    validate_entity,
+)
 
 __all__ = [
     "EntityMeta",
     "parse_entity_file",
     "parse_entity_directory",
+    # Schema
+    "ECONOMIC_ENTITY_SCHEMA",
+    "EntitySchema",
+    "EnumConstraint",
+    "SectionRequirement",
+    "SectionRule",
+    # Validator
+    "BatchComplianceResult",
+    "ComplianceDiagnostic",
+    "ComplianceResult",
+    "validate_entities",
+    "validate_entity",
 ]