Put all exceptions in their dedicated module.

src/tscut/exceptions.py

@@ -0,0 +1,23 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Copyright (C) 2026 Frédéric Tronel
+
+
+from typing import IO
+
+from typeguard import typechecked
+
+class TSCutError(Exception):
+    """Base exception for tscut."""
+
+
+class MissingToolError(TSCutError):
+    """Raised when a required external tool is unavailable."""
+
+
+class ExternalToolError(TSCutError):
+    """Raised when an external tool fails."""
+
+
+class InvalidMediaError(TSCutError):
+    """Raised when input media cannot be processed."""