chore: ruff auto-fix PLR6201 — tuple → set in membership tests (#23937)

Replace  with  for all literal-tuple
membership tests. Set lookup is O(1) vs O(n) for tuple — consistent
micro-optimization across the codebase.

608 instances fixed via `ruff --fix --unsafe-fixes`, 0 remaining.
133 files, +626/-626 (net zero).

environments/tool_context.py

@@ -179,7 +179,7 @@ class ToolContext:
 
         # Ensure parent directory exists in the sandbox
         parent = str(_Path(remote_path).parent)
-        if parent not in (".", "/"):
+        if parent not in {".", "/"}:
             self.terminal(f"mkdir -p {parent}", timeout=10)
 
         # For small files, single command is fine