feat: implement optimization #9 - release notes from CHANGELOG

Add release notes extraction from CHANGELOG for publishing:

- Create ChangelogParser class to extract version sections from CHANGELOG
- Support multiple output formats: markdown, plain text, HTML
- Add 'release notes VERSION' CLI command to extract notes
- Auto-detect latest version if not specified
- Support piping to gh/gitea release commands
- Save to file with --output option
- Plain text format removes markdown formatting
- HTML format converts markdown to HTML

This streamlines creating release notes for GitHub/Gitea releases
by extracting CHANGELOG content automatically.

Usage:
  release notes 0.10.0                    # Extract markdown notes
  release notes                           # Latest version
  release notes 0.10.0 --format plain    # Plain text
  release notes 0.10.0 -o notes.md       # Save to file
  release notes 0.10.0 | gh release create v0.10.0 -F -

🤖 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 ..changelog.parser import ChangelogParser
 from ..summary.generator import SummaryGenerator
 
 
@@ -358,5 +359,58 @@ def summary(ctx, version: str, output: Optional[Path]):
         sys.exit(1)
 
 
+@main.command('notes')
+@click.argument('version', required=False)
+@click.option('--format', 'output_format', type=click.Choice(['markdown', 'plain', 'html']),
+              default='markdown', help='Output format (default: markdown)')
+@click.option('--output', '-o', default=None, type=click.Path(path_type=Path),
+              help='Save to file instead of stdout')
+@click.pass_context
+def notes(ctx, version: Optional[str], output_format: str, output: Optional[Path]):
+    """Extract release notes from CHANGELOG.md.
+
+    Extracts the CHANGELOG section for a specific version and outputs it
+    in various formats. Useful for creating GitHub/Gitea release notes.
+
+    If no version is specified, uses the latest version from CHANGELOG.
+
+    Examples:
+        release notes 0.10.0              # Extract v0.10.0 notes (markdown)
+        release notes                     # Extract latest version notes
+        release notes 0.10.0 --format plain  # Plain text format
+        release notes 0.10.0 -o notes.md     # Save to file
+        release notes 0.10.0 | gh release create v0.10.0 -F -  # Pipe to gh
+    """
+    project_root = ctx.obj['project_root'] or Path.cwd()
+    changelog_path = project_root / 'CHANGELOG.md'
+
+    parser = ChangelogParser(changelog_path)
+
+    # Get version (use latest if not specified)
+    if version is None:
+        version = parser.get_latest_version()
+        if version is None:
+            print("❌ Could not determine version from CHANGELOG.md")
+            sys.exit(1)
+        print(f"Using latest version: {version}", file=sys.stderr)
+
+    # Extract content
+    content = parser.extract_version_section(version, format=output_format)
+
+    # Check for errors
+    if content.startswith("Error:") or content.startswith("Warning:"):
+        print(content)
+        sys.exit(1 if content.startswith("Error:") else 0)
+
+    # Output
+    if output:
+        if not output.is_absolute():
+            output = project_root / output
+        output.write_text(content)
+        print(f"✅ Release notes written to {output}", file=sys.stderr)
+    else:
+        print(content)
+
+
 if __name__ == '__main__':
     main()