Local Python executor ignores loop else clauses (for...else / while...else)

Describe the bug

smolagents.local_python_executor silently ignores the else clause of for and while loops. In Python, a loop's else block runs when the loop terminates normally (i.e. the iterator is exhausted or the while condition becomes false) and is skipped only when the loop is exited via break. The interpreter's evaluate_for and evaluate_while never look at the loop's orelse body, so the else block is never executed at all.

Because the executor is what runs CodeAgent-generated code, an agent that writes a perfectly valid for/else or while/else (a common idiom for search loops) gets a silently wrong result with no error.

Reproduction

from smolagents.local_python_executor import evaluate_python_code, BASE_PYTHON_TOOLS

code = """
x = 0
for i in range(3):
    x += i
else:
    x += 100
x
"""
result, _ = evaluate_python_code(code, static_tools=dict(BASE_PYTHON_TOOLS), state={})
print(result)   # prints 3  — CPython gives 103

The same happens with while ... else. Conversely, when the loop is broken out of, the else must be skipped (CPython behaviour), which the current code also cannot express because it returns/exits without distinguishing the two cases.

Expected behaviour

Match CPython:

• Loop completes normally (no break) → run the else block.
• Loop exits via break → skip the else block.
• continue does not affect whether the else runs.

Proposed fix

Track whether a break occurred in evaluate_for / evaluate_while, and execute the loop's orelse body when it did not. Happy to send a small PR with regression tests.