fix(ruff): propagate fix execution failures

[Kewe63]

Fixes #99

Functional change

RuffChecker.fix and RuffFormatter.fix previously accepted any Ruff process exit status. As a result, usage errors, invalid configuration, and runtime failures could be reported as successful Changeset results.

This change restores fail-closed execution for both fix operations.

Behavior preserved

• RuffChecker.fix still returns a Changeset when fixes are applied but ordinary lint violations remain.
• Remaining checker diagnostics are kept non-fatal through Ruff's --exit-zero option.
• Successful formatter and checker executions continue to return Changesets.
• Invalid arguments, configuration errors, and Ruff runtime failures now propagate as execution failures.

Implementation

• Remove expect=dagger.ReturnType.ANY from checker and formatter execution.
• Add --exit-zero only to ruff check --fix.
• Keep the formatter's default exit-code behavior unchanged.

Verification

• PYTHONPATH=ruff/src pytest -q ruff/tests — 37 passed after merging current main
• ruff check ruff/src ruff/tests — passed
• ruff format --check ruff/src ruff/tests — passed
• Unfixable checker findings with --exit-zero return exit 0
• Invalid checker and formatter arguments return exit 2

[danielgafni]

Sorry I was mass-closing PRs!

Please rewrite the PR description to address the functional change.

[Kewe63]

Updated the PR description to explicitly document the functional change and preserved behavior. I also merged the latest main; all CI checks are passing now.