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)).

plugins/memory/byterover/__init__.py

@@ -263,7 +263,7 @@ class ByteRoverMemoryProvider(MemoryProvider):
 
     def on_memory_write(self, action: str, target: str, content: str) -> None:
         """Mirror built-in memory writes to ByteRover."""
-        if action not in ("add", "replace") or not content:
+        if action not in {"add", "replace"} or not content:
             return
 
         def _write():
@@ -289,7 +289,7 @@ class ByteRoverMemoryProvider(MemoryProvider):
         for msg in messages[-10:]:  # last 10 messages
             role = msg.get("role", "")
             content = msg.get("content", "")
-            if isinstance(content, str) and content.strip() and role in ("user", "assistant"):
+            if isinstance(content, str) and content.strip() and role in {"user", "assistant"}:
                 parts.append(f"{role}: {content[:500]}")
 
         if not parts: