feat: implement optimization #7 - release summary auto-generation

Add automated release summary document generation:

- Create SummaryGenerator class to generate comprehensive release summaries
- Extract CHANGELOG sections for specific versions automatically
- Calculate git statistics (commits, files changed, insertions, deletions)
- List build artifacts from dist/ directory with sizes
- Include validation results in summary
- Add 'release summary VERSION' CLI command to generate summaries
- Support custom output paths with --output option
- Auto-detect project name from pyproject.toml
- Include contributor information from git log

This automates the manual task of creating release documentation,
ensuring consistent and comprehensive release summaries.

Usage:
  release summary 0.10.0                           # Generates RELEASE_SUMMARY_v0.10.0.md
  release summary 0.10.0 --output docs/v0.10.0.md  # Custom output path

🤖 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/cli/main.py

@@ -12,6 +12,7 @@ from typing import Optional
 from ..core.manager import ReleaseManager
 from ..utils.version import VersionManager
 from ..changelog.editor import ChangelogEditor
+from ..summary.generator import SummaryGenerator
 
 
 @click.group(invoke_without_command=True)
@@ -326,5 +327,36 @@ def prepare(ctx, version: str, date: Optional[str]):
         sys.exit(1)
 
 
+@main.command('summary')
+@click.argument('version')
+@click.option('--output', '-o', default=None, type=click.Path(path_type=Path),
+              help='Output file path (defaults to RELEASE_SUMMARY_vX.Y.Z.md)')
+@click.pass_context
+def summary(ctx, version: str, output: Optional[Path]):
+    """Generate release summary document.
+
+    Extracts CHANGELOG content, git statistics, build artifacts, and
+    validation results to create a comprehensive release summary.
+    """
+    project_root = ctx.obj['project_root'] or Path.cwd()
+
+    # Default output path
+    if output is None:
+        version_clean = version.lstrip('v')
+        output = project_root / f"RELEASE_SUMMARY_v{version_clean}.md"
+    elif not output.is_absolute():
+        output = project_root / output
+
+    generator = SummaryGenerator(project_root)
+
+    try:
+        content = generator.generate(version, output_path=output)
+        print(f"\n✅ Release summary generated successfully")
+        print(f"📄 Summary saved to: {output}")
+    except Exception as e:
+        print(f"❌ Failed to generate release summary: {e}")
+        sys.exit(1)
+
+
 if __name__ == '__main__':
     main()