refactor(benchmark): clean up resource registry bench per review

- remove unused imports (UTC, datetime, ResourceKind, SandboxStrategy)
- remove dead code (_bench_ulid, _CB32, _BENCH_CTR)
- use StaticPool for in-memory SQLite consistency

benchmarks/resource_registry_bench.py

@@ -12,7 +12,6 @@ Measures the performance of:
 from __future__ import annotations
 
 import sys
-from datetime import UTC, datetime
 from pathlib import Path
 from typing import Any
 
@@ -21,9 +20,7 @@ try:
         ResourceRegistryService,
     )
     from cleveragents.domain.models.core.resource_type import (
-        ResourceKind,
         ResourceTypeSpec,
-        SandboxStrategy,
     )
 except ModuleNotFoundError:
     sys.path.insert(0, str(Path(__file__).resolve().parents[1] / "src"))
@@ -31,9 +28,7 @@ except ModuleNotFoundError:
         ResourceRegistryService,
     )
     from cleveragents.domain.models.core.resource_type import (
-        ResourceKind,
         ResourceTypeSpec,
-        SandboxStrategy,
     )
 
 
@@ -41,10 +36,15 @@ def _setup_db() -> Any:
     """Create in-memory database and return session factory."""
     from sqlalchemy import create_engine, event
     from sqlalchemy.orm import sessionmaker
+    from sqlalchemy.pool import StaticPool
 
     from cleveragents.infrastructure.database.models import Base
 
-    engine = create_engine("sqlite:///:memory:")
+    engine = create_engine(
+        "sqlite:///:memory:",
+        connect_args={"check_same_thread": False},
+        poolclass=StaticPool,
+    )
 
     @event.listens_for(engine, "connect")
     def _fk(conn: Any, _rec: Any) -> None:
@@ -54,22 +54,6 @@ def _setup_db() -> Any:
     return sessionmaker(bind=engine)
 
 
-_CB32 = "0123456789ABCDEFGHJKMNPQRSTVWXYZ"
-_BENCH_CTR = 0
-
-
-def _bench_ulid() -> str:
-    """Generate a deterministic ULID-like string for benchmarks."""
-    global _BENCH_CTR  # noqa: PLW0603
-    _BENCH_CTR += 1
-    n = _BENCH_CTR
-    suffix = ""
-    for _ in range(7):
-        suffix = _CB32[n % 32] + suffix
-        n //= 32
-    return f"01HREGBNCH0AQDYTR4B{suffix}"[:26]
-
-
 class TypeSpecConstructionSuite:
     """Benchmark ResourceTypeSpec construction from config dicts."""