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/agent/test_context_compressor.py

@@ -1046,7 +1046,7 @@ class TestCompressWithClient:
         for i in range(1, len(result)):
             r1 = result[i - 1].get("role")
             r2 = result[i].get("role")
-            if r1 in ("user", "assistant") and r2 in ("user", "assistant"):
+            if r1 in {"user", "assistant"} and r2 in {"user", "assistant"}:
                 assert r1 != r2, f"consecutive {r1} at indices {i-1},{i}"
 
     def test_double_collision_merges_summary_into_tail(self):
@@ -1087,7 +1087,7 @@ class TestCompressWithClient:
         for i in range(1, len(result)):
             r1 = result[i - 1].get("role")
             r2 = result[i].get("role")
-            if r1 in ("user", "assistant") and r2 in ("user", "assistant"):
+            if r1 in {"user", "assistant"} and r2 in {"user", "assistant"}:
                 assert r1 != r2, f"consecutive {r1} at indices {i-1},{i}"
 
         # The summary text should be merged into the first tail message
@@ -1164,7 +1164,7 @@ class TestCompressWithClient:
         for i in range(1, len(result)):
             r1 = result[i - 1].get("role")
             r2 = result[i].get("role")
-            if r1 in ("user", "assistant") and r2 in ("user", "assistant"):
+            if r1 in {"user", "assistant"} and r2 in {"user", "assistant"}:
                 assert r1 != r2, f"consecutive {r1} at indices {i-1},{i}"
 
         # The summary should be merged into the first tail message (assistant at index 5)