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/refinement.py

@@ -0,0 +1,108 @@
+"""
+Refinement loop for iterative quality improvement.
+
+Implements FR-10: Halting and Refinement Policy
+Execute → Validate → Halt or Refine cycle.
+"""
+
+from typing import Callable, List, Optional, Tuple
+
+from markitect.prompts.quality.models import (
+    HaltDecision,
+    QualityPolicy,
+    RefinementResult,
+    ValidationResult,
+)
+from markitect.prompts.quality.policy import HaltingPolicyEngine
+from markitect.prompts.quality.validator import QualityValidator
+
+
+class RefinementLoop:
+    """
+    Iterative refinement loop with quality gate checks.
+
+    Executes a cycle of: execute → validate → check halting → refine
+    until a halting condition is met.
+    """
+
+    def __init__(
+        self,
+        validator: QualityValidator,
+        policy: QualityPolicy,
+    ):
+        """
+        Initialize with validator and policy.
+
+        Args:
+            validator: Quality validator with configured gates
+            policy: Halting policy configuration
+        """
+        self.validator = validator
+        self.policy = policy
+        self.policy_engine = HaltingPolicyEngine(policy)
+
+    def run(
+        self,
+        execution_callback: Callable[[int, List[ValidationResult]], Tuple[str, str, str]],
+        artifact_id: str,
+    ) -> RefinementResult:
+        """
+        Execute the refinement loop.
+
+        The execution_callback is called each iteration with:
+        - iteration number (1-based)
+        - previous validation results (empty list on first iteration)
+
+        It should return a tuple of (run_id, content, artifact_id).
+
+        Args:
+            execution_callback: Callable that executes/refines and returns
+                (run_id, content, artifact_id)
+            artifact_id: ID of the artifact being refined
+
+        Returns:
+            RefinementResult with complete iteration history
+        """
+        result = RefinementResult(iterations_run=0)
+        score_history: List[float] = []
+        prev_results: List[ValidationResult] = []
+
+        for iteration in range(1, self.policy.max_iterations + 1):
+            # Execute / refine
+            run_id, content, art_id = execution_callback(iteration, prev_results)
+            result.run_ids.append(run_id)
+
+            # Validate
+            current_results = self.validator.validate_artifact(
+                content, art_id, run_id=run_id if self.validator.db_path else None,
+            )
+            result.all_results.append(current_results)
+            result.iterations_run = iteration
+
+            # Evaluate halting
+            halting_record = self.policy_engine.evaluate(
+                results=current_results,
+                iteration=iteration,
+                score_history=score_history,
+                total_runs=len(result.run_ids),
+            )
+
+            current_score = self.policy_engine._aggregate_score(current_results)
+            score_history.append(current_score)
+
+            if halting_record.decision != HaltDecision.CONTINUE:
+                result.final_results = current_results
+                result.halting_record = halting_record
+                return result
+
+            prev_results = current_results
+
+        # Reached max iterations without explicit halt
+        result.final_results = prev_results
+        result.halting_record = self.policy_engine.evaluate(
+            results=prev_results,
+            iteration=self.policy.max_iterations,
+            score_history=score_history,
+            total_runs=len(result.run_ids),
+        )
+        return result