Fix PostgreSQL init_db: rollback after benign schema migration errors.

Co-authored-by: Cursor <cursoragent@cursor.com>

db_conn.py

@@ -92,6 +92,13 @@ def adapt_sql(sql: str) -> str:
 
 def is_benign_migration_error(exc: BaseException) -> bool:
     """ALTER TABLE 重复列等初始化迁移可忽略的错误。"""
+    if is_schema_migration_error(exc):
+        return True
+    return False
+
+
+def is_schema_migration_error(exc: BaseException) -> bool:
+    """init_db 增量迁移：缺表/缺列/重复列均可忽略。"""
     msg = str(exc).lower()
     if any(
         x in msg
@@ -99,18 +106,32 @@ def is_benign_migration_error(exc: BaseException) -> bool:
             "duplicate column",
             "already exists",
             "duplicate key",
+            "no such table",
+            "does not exist",
+            "undefined table",
+            "undefined column",
         )
     ):
         return True
-    if isinstance(exc, sqlite3.OperationalError) and "duplicate column" in msg:
+    if isinstance(exc, sqlite3.OperationalError) and (
+        "duplicate column" in msg or "no such table" in msg
+    ):
         return True
     if _PSYCOPG_OK and isinstance(exc, PgOperationalError):
         code = getattr(exc, "sqlstate", "") or ""
-        if code in ("42701", "42P07"):  # duplicate_column, duplicate_table
+        if code in ("42701", "42P07", "42P01", "42703"):
             return True
     return False
 
 
+def rollback_if_postgres(conn: "DbConnection") -> None:
+    if is_postgres():
+        try:
+            conn.rollback()
+        except Exception:
+            pass
+
+
 class DbCursor:
     """统一 cursor：兼容 sqlite3 的 execute / fetchone / lastrowid。"""