Linting and typing fixes.

src/tscut/exceptions.py

@@ -3,10 +3,6 @@
 # Copyright (C) 2026 Frédéric Tronel
 
 
-from typing import IO
-
-from typeguard import typechecked
-
 class TSCutError(Exception):
     """Base exception for tscut."""
 
@@ -21,3 +17,6 @@ class ExternalToolError(TSCutError):
 
 class InvalidMediaError(TSCutError):
     """Raised when input media cannot be processed."""
+
+class UnimplementedFeature(TSCutError):
+    """Raised when a rare feature is encountered and not yet implemented"""