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.

runner/harness/warmsnap.py

@@ -113,7 +113,9 @@ def _assert_undeployed(domain: str) -> None:
         )
 
 
-def snapshot(recipe: str, domain: str, commit: str | None = None, version: str | None = None) -> dict:
+def snapshot(
+    recipe: str, domain: str, commit: str | None = None, version: str | None = None
+) -> dict:
     """Take a last-known-good snapshot of every data volume of <domain>'s stack. The app MUST be
     undeployed. Atomically replaces the prior last-good. Returns the written meta dict."""
     _assert_undeployed(domain)
@@ -169,7 +171,9 @@ def restore(recipe: str, domain: str) -> dict:
     for vol in meta.get("volumes", []):
         tar_path = os.path.join(volumes_dir(recipe), f"{vol}.tar")
         if vol not in current:
-            raise SnapshotError(f"snapshot volume {vol} absent from current stack {sorted(current)}")
+            raise SnapshotError(
+                f"snapshot volume {vol} absent from current stack {sorted(current)}"
+            )
         mp = _volume_mountpoint(vol)
         # Clear the volume contents (incl. dotfiles) without removing the mountpoint itself.
         r = _run(["sh", "-c", f'rm -rf -- "{mp}"/* "{mp}"/.[!.]* "{mp}"/..?* 2>/dev/null; true'])