style: repo-wide lint pass — make the lint gate green again

Push builds have been RED on the lint step since ~build 209 from accumulated
formatting drift. This is the mechanical cleanup: ruff format + ruff --fix
(UP038 isinstance unions, SIM105 contextlib.suppress, UP031 f-strings, SIM115
tempfile context manager), shfmt -i 2 -ci, nixpkgs-fmt/statix/deadnix (merged
attrsets, dropped unused lib args), yamllint, and shell quoting fixes in
tests/lasuite-docs/setup_custom_tests.sh. No behaviour changes intended;
lint: PASS, unit tests: 138 passed.

tests/unit/test_http.py

@@ -126,9 +126,7 @@ def test_http_get_transport_failure_returns_status_zero():
 
 
 def test_http_get_sends_headers(server):
-    status, body = harness_http.http_get(
-        f"{server}/echo-headers", headers={"X-Auth": "token-123"}
-    )
+    status, body = harness_http.http_get(f"{server}/echo-headers", headers={"X-Auth": "token-123"})
     assert status == 200
     assert body["X-Auth"] == "token-123"