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/cli/test_reasoning_command.py

@@ -70,7 +70,7 @@ class TestHandleReasoningCommand(unittest.TestCase):
         stub = self._make_cli(show_reasoning=False)
         # Simulate /reasoning show
         arg = "show"
-        if arg in ("show", "on"):
+        if arg in {"show", "on"}:
             stub.show_reasoning = True
             stub.agent.reasoning_callback = lambda x: None
         self.assertTrue(stub.show_reasoning)
@@ -79,7 +79,7 @@ class TestHandleReasoningCommand(unittest.TestCase):
         stub = self._make_cli(show_reasoning=True)
         # Simulate /reasoning hide
         arg = "hide"
-        if arg in ("hide", "off"):
+        if arg in {"hide", "off"}:
             stub.show_reasoning = False
             stub.agent.reasoning_callback = None
         self.assertFalse(stub.show_reasoning)
@@ -88,14 +88,14 @@ class TestHandleReasoningCommand(unittest.TestCase):
     def test_on_enables_display(self):
         stub = self._make_cli(show_reasoning=False)
         arg = "on"
-        if arg in ("show", "on"):
+        if arg in {"show", "on"}:
             stub.show_reasoning = True
         self.assertTrue(stub.show_reasoning)
 
     def test_off_disables_display(self):
         stub = self._make_cli(show_reasoning=True)
         arg = "off"
-        if arg in ("hide", "off"):
+        if arg in {"hide", "off"}:
             stub.show_reasoning = False
         self.assertFalse(stub.show_reasoning)