feat(prompts): implement Phase 7 - Quality & Validation (FR-9, FR-10)

Add quality gate framework with schema validation (JSON Schema via
jsonschema library), pattern validation (regex-based), multi-gate
QualityValidator with SQLite persistence, HaltingPolicyEngine with
budget/iteration/improvement checks, and RefinementLoop for iterative
execute-validate-halt cycles.

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

markitect/prompts/quality/__init__.py

@@ -0,0 +1,53 @@
+"""
+Quality validation and halting policies for prompt artifacts.
+
+Implements FR-9: QualityGate Validation
+Implements FR-10: Halting and Refinement Policy
+
+- FR-9.1: Schema validation against generated artifacts
+- FR-9.2: Multiple QualityGates per artifact
+- FR-9.3: Record pass/fail results and diagnostics
+- FR-9.4: Halting policies based on QualityGate results
+- FR-10.1: Configurable QualityPolicies
+- FR-10.2: Halting decisions (quality, improvement, iterations, budget)
+- FR-10.3: Record halting decisions in RunManifest
+"""
+
+from markitect.prompts.quality.models import (
+    GateType,
+    ValidationStatus,
+    HaltDecision,
+    ValidationDiagnostic,
+    ValidationResult,
+    QualityGate,
+    QualityPolicy,
+    HaltingRecord,
+    RefinementResult,
+)
+from markitect.prompts.quality.gates.schema_gate import SchemaValidationGate
+from markitect.prompts.quality.gates.pattern_gate import PatternValidationGate
+from markitect.prompts.quality.validator import QualityValidator
+from markitect.prompts.quality.policy import HaltingPolicyEngine
+from markitect.prompts.quality.refinement import RefinementLoop
+
+__all__ = [
+    # Models
+    "GateType",
+    "ValidationStatus",
+    "HaltDecision",
+    "ValidationDiagnostic",
+    "ValidationResult",
+    "QualityGate",
+    "QualityPolicy",
+    "HaltingRecord",
+    "RefinementResult",
+    # Gates
+    "SchemaValidationGate",
+    "PatternValidationGate",
+    # Validator
+    "QualityValidator",
+    # Policy
+    "HaltingPolicyEngine",
+    # Refinement
+    "RefinementLoop",
+]