fix: resolve all flake8 lint errors (118 → 0)

src/blackboard/db.py

@@ -4,7 +4,6 @@ from __future__ import annotations
 
 import sqlite3
 from pathlib import Path
-from typing import Optional
 
 
 def init_db(db_path: Path) -> None:

src/blackboard/models.py

@@ -3,7 +3,7 @@
 from __future__ import annotations
 
 from dataclasses import dataclass, field
-from typing import Any, Dict, List, Optional
+from typing import Any, List, Optional
 
 
 @dataclass

src/blackboard/operations.py

@@ -11,7 +11,6 @@ from typing import Any, Dict, List, Optional
 
 from .db import (
     VALID_TRANSITIONS,
-    VALID_STATUSES,
     COMMENT_TYPES,
     EVENT_TYPES,
     OUTPUT_TYPES,
@@ -693,7 +692,6 @@ class Blackboard:
         finally:
             conn.close()
 
-
     # ── Checkpoint CRUD（M3） ──
 
     def create_checkpoint(

src/blackboard/registry.py

@@ -355,4 +355,3 @@ class ProjectRegistry:
 
     def reload(self) -> None:
         """兼容旧接口（SQLite 不需要 reload cache）"""
-        pass