feat(help): enhance CLI help rendering with Panels and TLDR validation

- Updated `Command.help_signature` to return a `(Panel, description)` tuple,
  enabling richer Rich-based help output with formatted panels.
- Integrated `program` context into commands to display accurate CLI invocation
  (`falyx run …`) depending on mode (RUN, PREVIEW, RUN_ALL).
- Refactored `_show_help` to print `Panel`-styled usage and descriptions instead
  of table rows.
- Added `program` and `options_manager` propagation to built-in commands
  (Exit, History, Help) for consistent CLI display.
- Improved `CommandArgumentParser.add_tldr_examples()` with stricter validation
  (`all()` instead of `any()`), and added new TLDR tests for coverage.
- Simplified parser epilog text to `Tip: Use 'falyx run ?' to show available commands.`
- Added tests for required `Argument` fields and TLDR examples.
- Bumped version to 0.1.73.

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "falyx"
-version = "0.1.72"
+version = "0.1.73"
 description = "Reliable and introspectable async CLI action framework."
 authors = ["Roland Thomas Jr <roland@rtj.dev>"]
 license = "MIT"