feat: add TLDR ArgumentAction and Rich-compatible prompt styling

- Introduce `ArgumentAction.TLDR` for showing concise usage examples
- Add `rich_text_to_prompt_text()` to support Rich-style markup in all prompt_toolkit inputs
- Migrate all prompt-based Actions to use `prompt_message` with Rich styling support
- Standardize `CancelSignal` as the default interrupt behavior for prompt-driven Actions

examples/falyx_demo.py

@@ -84,7 +84,7 @@ async def main() -> None:
 
     # --- Bottom bar info ---
     flx.bottom_bar.columns = 3
-    flx.bottom_bar.add_toggle_from_option("V", "Verbose", flx.options, "verbose")
+    flx.bottom_bar.add_toggle_from_option("B", "Verbose", flx.options, "verbose")
     flx.bottom_bar.add_toggle_from_option("U", "Debug Hooks", flx.options, "debug_hooks")
     flx.bottom_bar.add_static("Version", f"Falyx v{__version__}")