fixed a bug with the test-repo skill that created an invalid session file

[Soph]

When using the test-repo skill (for example "Can you do a test of the auto-commit strategy with the test-repo skill") it creates fake claude sessions. Starting claude code after such a test showed an error like this on start:

This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). The promise rejected with the reason:
RangeError: Invalid Date
    at toISOString (unknown)

The skill is now generating properly formatted session logs.