Autosave interrupted interactive sessions

[nhicks00]

Summary

Fixes autosave persistence for interrupted Code Puppy sessions.

If a user cancels an agent run with Ctrl-C and then exits, the interactive loop previously skipped the normal autosave path because cancelled runs return None and immediately continue to the next prompt. That could leave the autosave file missing the latest in-memory conversation history.

What Changed

• Adds a small _save_autosave_snapshot() helper around auto_save_session_if_enabled().
• Saves immediately before returning to the prompt after a cancelled agent run.
• Saves once during CLI shutdown so Ctrl-D, /exit, top-level interrupt, or process cleanup has a final persistence attempt.
• Saves from single-prompt mode in finally as a defensive cleanup path.
• Adds test coverage for the cancelled interactive prompt path.

Validation

uv run pytest --no-cov tests/test_cli_runner_coverage.py tests/test_cli_runner_full_coverage.py -q
uv run ruff check code_puppy/cli_runner.py tests/test_cli_runner_full_coverage.py
uv run ruff format --check code_puppy/cli_runner.py tests/test_cli_runner_full_coverage.py

Results:

• 73 passed
• Ruff check passed
• Ruff format check passed

[mpfaffenberger]

This looks straightforward - merge?