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/gates/pattern_gate.py

@@ -0,0 +1,109 @@
+"""
+Pattern validation quality gate.
+
+Validates content against required and forbidden regex patterns.
+"""
+
+import re
+import uuid
+from typing import List, Optional
+
+from markitect.prompts.quality.models import (
+    GateType,
+    QualityGate,
+    ValidationDiagnostic,
+    ValidationResult,
+    ValidationStatus,
+)
+
+
+class PatternValidationGate(QualityGate):
+    """
+    Validates artifact content against regex patterns.
+
+    Checks that all required patterns are present and no forbidden
+    patterns are found.
+    """
+
+    def __init__(
+        self,
+        required_patterns: Optional[List[str]] = None,
+        forbidden_patterns: Optional[List[str]] = None,
+        gate_id: Optional[str] = None,
+        name: str = "pattern",
+    ):
+        """
+        Initialize with pattern lists.
+
+        Args:
+            required_patterns: Regex patterns that must be found in content
+            forbidden_patterns: Regex patterns that must NOT be found in content
+            gate_id: Optional gate identifier
+            name: Human-readable gate name
+        """
+        super().__init__(
+            gate_id=gate_id or str(uuid.uuid4()),
+            name=name,
+            gate_type=GateType.PATTERN,
+        )
+        self.required_patterns = required_patterns or []
+        self.forbidden_patterns = forbidden_patterns or []
+
+    def validate(self, content: str, artifact_id: str) -> ValidationResult:
+        """
+        Validate content against required and forbidden patterns.
+
+        Args:
+            content: Content string to validate
+            artifact_id: ID of the artifact being validated
+
+        Returns:
+            ValidationResult with status and diagnostics
+        """
+        diagnostics = []
+        total_checks = len(self.required_patterns) + len(self.forbidden_patterns)
+        failures = 0
+
+        # Check required patterns
+        for pattern in self.required_patterns:
+            if not re.search(pattern, content):
+                diagnostics.append(
+                    ValidationDiagnostic(
+                        code="MISSING_PATTERN",
+                        message=f"Required pattern not found: {pattern}",
+                        severity="error",
+                    )
+                )
+                failures += 1
+
+        # Check forbidden patterns
+        for pattern in self.forbidden_patterns:
+            match = re.search(pattern, content)
+            if match:
+                diagnostics.append(
+                    ValidationDiagnostic(
+                        code="FORBIDDEN_PATTERN",
+                        message=f"Forbidden pattern found: {pattern} (matched: '{match.group()}')",
+                        severity="error",
+                    )
+                )
+                failures += 1
+
+        if total_checks == 0:
+            status = ValidationStatus.PASS
+            score = 1.0
+        elif failures == 0:
+            status = ValidationStatus.PASS
+            score = 1.0
+        else:
+            status = ValidationStatus.FAIL
+            score = max(0.0, 1.0 - failures / total_checks)
+
+        return ValidationResult.create(
+            gate_id=self.id,
+            gate_type=self.gate_type,
+            artifact_id=artifact_id,
+            status=status,
+            score=score,
+            diagnostics=diagnostics,
+        )