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/ghost/functional/test_post_roundtrip.py

@@ -43,17 +43,17 @@ def test_create_post_roundtrip(live_app):
     title = f"ccci-marker-{uniq}"
     marker = f"ccci-body-marker-{uniq}-roundtrip"
     created = admin.create_post(title, f"<p>{marker}</p>")
-    assert created.get("title") == title, (
-        f"created post title mismatch: sent {title!r}, got {created.get('title')!r}"
-    )
+    assert (
+        created.get("title") == title
+    ), f"created post title mismatch: sent {title!r}, got {created.get('title')!r}"
 
     # 4) Read it back by id and assert the post survived the round-trip (title always returned;
     #    html returned because we requested ?formats=html).
     got = admin.get_post(created["id"])
-    assert got.get("title") == title, (
-        f"post title did not round-trip: sent {title!r}, got {got.get('title')!r}"
-    )
+    assert (
+        got.get("title") == title
+    ), f"post title did not round-trip: sent {title!r}, got {got.get('title')!r}"
     html = got.get("html") or ""
-    assert marker in html, (
-        f"post body did not round-trip: marker {marker!r} not in read-back html {html!r}"
-    )
+    assert (
+        marker in html
+    ), f"post body did not round-trip: marker {marker!r} not in read-back html {html!r}"