test(sandbox): fix the lint findings in the SmolVM tests

[AlexS-scale]

What and why

main fails the unit check since #157 (run). The CI of #157 ran before #192 added the lint step, so it did not find the 6 findings that #157 adds. Only the Lint step fails. Thus each pull request fails unit, and #193 does not publish the versions after #157 to PyPI.

• tst/manual/smol_vm_agent_check.py and tst/manual/smol_vm_gateway_check.py import the local_stack fixture with noqa: F401, so pyflakes reads each test that requests it as a redefinition (F811, 5 findings). They now import it with a same-name alias, as ci: lint with ruff's pyflakes rules, and fix what they find #192 did for the other modules that import this fixture.
• smol_vm_provider_test.py has an f-string without placeholders (F541). It is now a plain string.

How it was tested

• ruff check: no findings.
• The alias binds the same name, so pytest finds the fixture as before. The manual checks need the smol extra to be collected, with or without this change.

Confidence Score: 5/5

The PR appears safe to merge; the three edits preserve test behavior.

Summary

Fixes six lint findings in the SmolVM tests without changing their behavior.

• SmolVM test files clear lint findings without changing test behavior.

_{Reviews (1) · Last reviewed commit: "test(sandbox): fix the lint findings in ..." · Reviewed by Greptile}