fix: include commands in package distribution

Fixed "Command source directory not found" error when installing via pipx.

Changes:
- Copied command files from plugins/superclaude/commands/ to src/superclaude/commands/
- Updated pyproject.toml to include commands in wheel package
- Added README.md explaining command sync requirement
- install_commands.py already had fallback logic to check package_root/commands/

The commands directory will be included in the installed package, allowing
'superclaude install' to work correctly from pipx installations.

Note: In v4.x, commands must be synced between plugins/ and src/superclaude/.
In v5.0, the plugin system will use plugins/ directly.

Fixes installation error:
  Command source directory not found: /path/to/plugins/superclaude/commands

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

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

pyproject.toml

@@ -70,6 +70,7 @@ superclaude = "superclaude.pytest_plugin"
 packages = ["src/superclaude"]
 include = [
     "src/superclaude/skills/confidence-check/**",
+    "src/superclaude/commands/**/*.md",
 ]
 
 [tool.hatch.build.targets.sdist]