chore: ruff auto-fix PLR6201 resweep — tuple → set in membership tests (#27355)

Six days after #23937 (608 fixes) the codebase had accumulated 241 new
PLR6201 violations. Same mechanical `x in (...)` → `x in {...}` fix,
same zero-risk profile: set lookup is O(1) vs O(n) for tuple and the
two are semantically equivalent for hashable scalar membership tests.

All 241 instances fixed via `ruff check --select PLR6201 --fix
--unsafe-fixes`, zero remaining. Every changed value is a hashable
scalar (str/int/None/enum/signal); no risk of unhashable runtime
errors. No behavior change.

Test plan:
- 119 files changed, +244/-244 (net zero) — exactly one-line edits
- `ruff check` clean afterward
- Compile checks pass on the largest touched files (cli.py, run_agent.py,
  gateway/run.py, gateway/platforms/discord.py, model_tools.py)
- Subset broad test run on tests/gateway/ tests/hermes_cli/ tests/agent/
  tests/tools/: 18187 passed, 59 pre-existing failures (verified against
  origin/main with the same shape — identical failure count, identical
  category — all xdist test-order flakes unrelated to this change)

Follows the same template as PR #23937 ([tracker: #23972](https://github.com/NousResearch/hermes-agent/issues/23972)).

tests/hermes_cli/test_memory_reset.py

@@ -43,9 +43,9 @@ def _run_memory_reset(target="all", yes=False, monkeypatch=None, confirm_input="
 
     mem_dir = get_hermes_home() / "memories"
     files_to_reset = []
-    if target in ("all", "memory"):
+    if target in {"all", "memory"}:
         files_to_reset.append(("MEMORY.md", "agent notes"))
-    if target in ("all", "user"):
+    if target in {"all", "user"}:
         files_to_reset.append(("USER.md", "user profile"))
 
     existing = [(f, desc) for f, desc in files_to_reset if (mem_dir / f).exists()]