feat: add versioning infrastructure and release script

- Fix version mismatch: __init__.py had 'v1.0.0', pyproject.toml had '0.1.0'
  Now both use '0.1.0' (no v prefix — added in display code only)
- Add __release_date__ for CalVer date tracking alongside SemVer version
- Fix double-v bug in cmd_version (was printing 'vv1.0.0')
- Update banner title to show 'Hermes Agent v0.1.0 (2026.3.12)' format
- Update cli.py banner to match new format
- Add scripts/release.py: full release automation tool
  - Generates categorized changelogs from git history
  - Maps git authors to GitHub @mentions (70+ contributors)
  - Supports dry-run preview and --publish mode
  - Creates annotated CalVer git tags + GitHub Releases
  - Bumps semver in source files automatically
  - Usage: python scripts/release.py --bump minor --publish
- Add .release_notes.md to .gitignore

Versioning scheme: CalVer tags (v2026.3.12) + SemVer display (v0.1.0)

hermes_cli/banner.py

@@ -62,7 +62,7 @@ def _skin_branding(key: str, fallback: str) -> str:
 # ASCII Art & Branding
 # =========================================================================
 
-from hermes_cli import __version__ as VERSION
+from hermes_cli import __version__ as VERSION, __release_date__ as RELEASE_DATE
 
 HERMES_AGENT_LOGO = """[bold #FFD700]██╗  ██╗███████╗██████╗ ███╗   ███╗███████╗███████╗       █████╗  ██████╗ ███████╗███╗   ██╗████████╗[/]
 [bold #FFD700]██║  ██║██╔════╝██╔══██╗████╗ ████║██╔════╝██╔════╝      ██╔══██╗██╔════╝ ██╔════╝████╗  ██║╚══██╔══╝[/]
@@ -380,7 +380,7 @@ def build_welcome_banner(console: Console, model: str, cwd: str,
     border_color = _skin_color("banner_border", "#CD7F32")
     outer_panel = Panel(
         layout_table,
-        title=f"[bold {title_color}]{agent_name} {VERSION}[/]",
+        title=f"[bold {title_color}]{agent_name} v{VERSION} ({RELEASE_DATE})[/]",
         border_style=border_color,
         padding=(0, 2),
     )