feat: implement optimization #3 - CHANGELOG validation in release flow

Add comprehensive CHANGELOG validation to release validation process:

- Add _validate_changelog() method that validates CHANGELOG.md against
  changelog-schema-v1.0.md using markitect validate --semantic
- Add validate_changelog_version() to check version section exists with
  proper date format and Unreleased section
- Add check_version_tag_consistency() to verify CHANGELOG versions
  match git tags
- Integrate CHANGELOG validation into validate_release_state()
- Add CHANGELOG-specific recommendations to _get_recommendations()

This prevents releases with invalid or inconsistent CHANGELOG files,
catching format errors before they become problems.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

capabilities/release-management/src/release_management/utils/validation.py

@@ -4,6 +4,7 @@ Release validation utilities.
 This module provides validation functions for release readiness.
 """
 
+import subprocess
 from pathlib import Path
 from typing import List, Tuple, Optional
 
@@ -48,6 +49,10 @@ class ReleaseValidator:
         config_issues = self._validate_configuration()
         issues.extend(config_issues)
 
+        # CHANGELOG validation
+        changelog_issues = self._validate_changelog()
+        issues.extend(changelog_issues)
+
         return len(issues) == 0, issues
 
     def _validate_git_state(self) -> List[str]:
@@ -186,6 +191,117 @@ class ReleaseValidator:
 
         return len(issues) == 0, issues
 
+    def _validate_changelog(self) -> List[str]:
+        """Validate CHANGELOG.md using changelog schema.
+
+        Returns:
+            List of CHANGELOG-related issues
+        """
+        issues = []
+        changelog_path = self.project_root / 'CHANGELOG.md'
+
+        # Check if CHANGELOG exists
+        if not changelog_path.exists():
+            issues.append("Missing CHANGELOG.md file")
+            return issues
+
+        # Check if changelog schema exists
+        schema_path = self.project_root / 'markitect' / 'schemas' / 'changelog-schema-v1.0.md'
+        if not schema_path.exists():
+            # Schema doesn't exist, skip validation
+            return issues
+
+        # Validate CHANGELOG with schema using markitect validate command
+        try:
+            result = subprocess.run(
+                [
+                    'markitect', 'validate', str(changelog_path),
+                    '--schema', str(schema_path),
+                    '--semantic'
+                ],
+                capture_output=True,
+                text=True,
+                cwd=self.project_root
+            )
+
+            if result.returncode != 0:
+                issues.append("CHANGELOG.md validation failed against schema")
+                # Parse output for specific errors
+                if 'Unreleased section' in result.stdout:
+                    issues.append("  - Missing [Unreleased] section in CHANGELOG")
+                if 'version format' in result.stdout.lower():
+                    issues.append("  - Invalid version format in CHANGELOG")
+
+        except FileNotFoundError:
+            # markitect command not available
+            issues.append("Cannot validate CHANGELOG (markitect command not found)")
+        except Exception as e:
+            issues.append(f"Error validating CHANGELOG: {e}")
+
+        return issues
+
+    def validate_changelog_version(self, version: str) -> Tuple[bool, List[str]]:
+        """Validate that CHANGELOG has section for specified version.
+
+        Args:
+            version: Version to check (e.g., "0.10.0")
+
+        Returns:
+            Tuple of (is_valid, list_of_issues)
+        """
+        issues = []
+        changelog_path = self.project_root / 'CHANGELOG.md'
+
+        if not changelog_path.exists():
+            issues.append("CHANGELOG.md not found")
+            return False, issues
+
+        try:
+            content = changelog_path.read_text()
+
+            # Check for version section
+            version_header = f"## [{version}]"
+            if version_header not in content:
+                issues.append(f"CHANGELOG missing section for version {version}")
+
+            # Check for Unreleased section
+            if "## [Unreleased]" not in content:
+                issues.append("CHANGELOG missing [Unreleased] section")
+
+            # Check if version section has a date
+            import re
+            date_pattern = rf"## \[{re.escape(version)}\] - \d{{4}}-\d{{2}}-\d{{2}}"
+            if not re.search(date_pattern, content):
+                issues.append(f"Version {version} section missing date or has invalid date format")
+
+        except Exception as e:
+            issues.append(f"Error reading CHANGELOG: {e}")
+
+        return len(issues) == 0, issues
+
+    def check_version_tag_consistency(self, version: str) -> Tuple[bool, List[str]]:
+        """Check consistency between CHANGELOG version and git tags.
+
+        Args:
+            version: Version to check (e.g., "0.10.0")
+
+        Returns:
+            Tuple of (is_consistent, list_of_issues)
+        """
+        issues = []
+
+        # Check CHANGELOG has the version
+        changelog_valid, changelog_issues = self.validate_changelog_version(version)
+        if not changelog_valid:
+            issues.extend(changelog_issues)
+
+        # Check git tag exists
+        tag_name = version if version.startswith('v') else f'v{version}'
+        if not self.git_manager.tag_exists(tag_name):
+            issues.append(f"Git tag {tag_name} doesn't exist for version in CHANGELOG")
+
+        return len(issues) == 0, issues
+
     def get_validation_summary(self) -> dict:
         """Get a comprehensive validation summary.
 
@@ -224,6 +340,10 @@ class ReleaseValidator:
         if any('authentication' in issue.lower() for issue in issues):
             recommendations.append("Set up authentication tokens for package publishing")
 
+        if any('CHANGELOG' in issue for issue in issues):
+            recommendations.append("Fix CHANGELOG.md format and ensure [Unreleased] section exists")
+            recommendations.append("Validate with: markitect validate CHANGELOG.md --schema changelog-schema-v1.0.md --semantic")
+
         if not issues:
             recommendations.append("Repository is ready for release!")