feat(config): add /config TUI with tab-based settings and plugin config framework

- textual-based ConfigApp with General, Plugins, and per-plugin tabs
- GeneralConfig (user_name, assistant_name) + plugin_settings dict added to PyraConfig
- ConfigField dataclass and config_fields() method added to plugin protocol
- /config slash command in chat REPL launches the TUI
- pyra auto-runs setup wizard on first invocation when no config.yaml exists
- CLAUDE.md updated with config_fields() plugin guide and Code Inventory entries

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -17,6 +17,7 @@ dependencies = [
     "pydantic>=2.0.0",
     "httpx>=0.27.0",
     "python-dotenv>=1.0.0",
+    "textual>=1.0.0",
 ]
 
 [project.optional-dependencies]