fix(logging[doctest]): add doctest to _identity

why: All functions must have working doctests per project conventions.
what:
- Add Examples section with string and integer pass-through tests

Author: tony

src/tmuxp/_compat.py

@@ -11,7 +11,22 @@
 
 
 def _identity(x: object) -> object:
-    """Return *x* unchanged — used as a no-op decorator."""
+    """Return *x* unchanged — used as a no-op decorator.
+
+    Examples
+    --------
+    >>> from tmuxp._compat import _identity
+
+    Strings pass through unchanged:
+
+    >>> _identity("hello")
+    'hello'
+
+    Integers pass through unchanged:
+
+    >>> _identity(42)
+    42
+    """
     return x