refactor: refine CLI options and enhance debug logging

- Remove --mode, --transition-type, and --decay-index CLI flags
  (parameters now come from ENSDF data or custom JSON input)
- Clarify energy units in all CLI help text (MeV throughout, keV for detector params)
- Enhance logging verbosity:
  - -v (INFO): shows source, component initialization, workflow steps
  - -vv (DEBUG): shows detailed internals of all spectrum components
    (parameters, evaluation counts, input/output ranges)
- Improve CSV headers with element notation (e.g. Tc99 -> Ru99)
- Add CONVENTIONS.md documenting energy unit and logging conventions
- Update TODO.md with completion status

beta_spectrum/base.py

@@ -23,6 +23,14 @@ class SpectrumComponent(ABC):
 
     def __init__(self, logger: Optional["logging.Logger"] = None) -> None:
         self._logger = logger
+        self._log_component_info()
+
+    def _log_component_info(self) -> None:
+        """Log component identification at INFO level."""
+        if self._logger is None:
+            return
+        class_name = self.__class__.__name__
+        self._logger.info("Component initialized: %s", class_name)
 
     @abstractmethod
     def __call__(self, W: ArrayLike) -> ArrayLike: