fix: python3 compatibility in shell hand tests (#56)

- Use sys.executable instead of hardcoded "python" in tests
- Fixes test_run_python_expression and test_run_nonzero_exit
- Passes allowed_prefixes for both python and python3

tests/test_hands_shell.py

@@ -10,6 +10,7 @@ Covers:
 """
 
 import asyncio
+import sys
 
 import pytest
 
@@ -91,8 +92,10 @@ async def test_run_python_expression():
     """Running a python one-liner should succeed."""
     from infrastructure.hands.shell import ShellHand
 
-    hand = ShellHand()
+    # Allow both 'python' and 'python3' (sys.executable basename)
-    result = await hand.run("python -c 'print(2 + 2)'")
+    allowed = ("python", "python3")
+    hand = ShellHand(allowed_prefixes=allowed)
+    result = await hand.run(f"{sys.executable} -c 'print(2 + 2)'")
     assert result.success is True
     assert "4" in result.stdout
 
@@ -118,8 +121,10 @@ async def test_run_nonzero_exit():
     """A command that exits non-zero should return success=False."""
     from infrastructure.hands.shell import ShellHand
 
-    hand = ShellHand()
+    # Allow both 'python' and 'python3' (sys.executable basename)
-    result = await hand.run("python -c 'import sys; sys.exit(1)'")
+    allowed = ("python", "python3")
+    hand = ShellHand(allowed_prefixes=allowed)
+    result = await hand.run(f"{sys.executable} -c 'import sys; sys.exit(1)'")
     assert result.success is False
     assert result.exit_code == 1