chore(tests): fix ruff lint violations in tests/ (#2827)

Clear pre-existing lint debt flagged by repo-wide `ruff check` (the lint
config only scopes src/, so tests/ had drifted). No behavior change.

- F401/F541: drop unused imports and redundant f-string prefixes (autofix)
- E741: rename ambiguous `l` to `ln` in comprehensions
- E702: split semicolon-joined statements onto separate lines
- F841: drop unused bindings while keeping the side-effecting calls
  (_minimal_feature, install_from_directory)

Full suite: 3344 passed, 40 skipped. ruff check (repo-wide): clean.

tests/integrations/test_integration_subcommand.py

@@ -3,7 +3,6 @@
 import json
 import os
 
-import pytest
 from typer.testing import CliRunner
 
 from specify_cli import app