fix(find-field): 修两个 MySQL 兼容 bug

1. MySQL 8.0 INFORMATION_SCHEMA.COLUMNS 没有 TABLE_COMMENT 列
   - 原查询 SELECT TABLE_COMMENT FROM INFORMATION_SCHEMA.COLUMNS 直接报 1054
   - 改成 LEFT JOIN INFORMATION_SCHEMA.TABLES 拿表注释

2. schema/table 名含 '-' 时 quote_ident 校验失败
   - web3/backend/core/db_adapter.py::quote_ident 用 ^[A-Za-z_][A-Za-z0-9_]*$ 校验
   - 但 MySQL 的 schema/table 名合法可含 '-', 只要用反引号包即可
   - 仅在 skill 脚本 table_row_count() 里给 MySQL 分支走自定义 _safe_mysql_ident,
     其他方言照旧用 quote_ident, 不动通用 db_adapter 逻辑

触发场景: 查 smart-build 库时直接报错; 修完后能正常输出 6 张含 credit_code/uscc 的表
附加: 踩坑已记录到 memory (mysql-information-schema-columns-no-table-comment)

.claude/skills/find-field/scripts/find_field.py

@@ -127,22 +127,27 @@ def _build_oracle_match_sql(keywords: list[str]) -> tuple[str, tuple]:
 
 
 def _build_mysql_match_sql(keywords: list[str], database: str) -> tuple[str, tuple]:
-    """MySQL 走 INFORMATION_SCHEMA.COLUMNS（database_name 不需要 UPPER，默认就是）"""
-    like_clause = " OR ".join([f"LOWER(COLUMN_NAME) LIKE %s" for _ in keywords])
+    """MySQL 走 INFORMATION_SCHEMA.COLUMNS（database_name 不需要 UPPER，默认就是）。
+    注意：MySQL 8.0 的 COLUMNS 表里没有 TABLE_COMMENT（它在 TABLES 里），需要 LEFT JOIN。
+    """
+    like_clause = " OR ".join([f"LOWER(c.COLUMN_NAME) LIKE %s" for _ in keywords])
     sql = f"""
         SELECT
-            TABLE_SCHEMA                                       AS owner,
-            TABLE_NAME                                         AS table_name,
-            COLUMN_NAME                                        AS column_name,
-            COLUMN_TYPE                                        AS column_type,
-            IS_NULLABLE                                        AS nullable,
-            COLUMN_DEFAULT                                     AS column_default,
-            COLUMN_COMMENT                                     AS column_comment,
-            TABLE_COMMENT                                      AS table_comment
-        FROM INFORMATION_SCHEMA.COLUMNS
-        WHERE TABLE_SCHEMA = %s
+            c.TABLE_SCHEMA                                     AS owner,
+            c.TABLE_NAME                                       AS table_name,
+            c.COLUMN_NAME                                      AS column_name,
+            c.COLUMN_TYPE                                      AS column_type,
+            c.IS_NULLABLE                                      AS nullable,
+            c.COLUMN_DEFAULT                                   AS column_default,
+            c.COLUMN_COMMENT                                   AS column_comment,
+            t.TABLE_COMMENT                                    AS table_comment
+        FROM INFORMATION_SCHEMA.COLUMNS c
+        LEFT JOIN INFORMATION_SCHEMA.TABLES t
+          ON t.TABLE_SCHEMA = c.TABLE_SCHEMA
+         AND t.TABLE_NAME   = c.TABLE_NAME
+        WHERE c.TABLE_SCHEMA = %s
           AND ({like_clause})
-        ORDER BY TABLE_NAME, ORDINAL_POSITION
+        ORDER BY c.TABLE_NAME, c.ORDINAL_POSITION
     """
     params = (database,) + tuple(f"%{kw.lower()}%" for kw in keywords)
     return sql, params
@@ -189,10 +194,22 @@ def _build_dameng_match_sql(keywords: list[str]) -> tuple[str, tuple]:
 
 # ── 3. 行数 + 视图溯源 ─────────────────────────
 def table_row_count(db: DBConnection, owner: str, table_name: str, db_type: str) -> int | str:
-    """跨方言 COUNT(*)。owner.table 用对应方言的 quote。"""
-    from web3.backend.core.db_adapter import quote_ident
-    ident_owner = quote_ident(owner, db_type)
-    ident_tbl = quote_ident(table_name, db_type)
+    """跨方言 COUNT(*)。owner.table 用对应方言的 quote。
+    MySQL 的 schema / table 名允许含 `-`（比如 `smart-build`），用反引号包即可；
+    db_adapter.quote_ident 太严格，这里自己处理 MySQL 的宽松标识符。
+    """
+    def _safe_mysql_ident(name: str) -> str:
+        if "`" in name or "\n" in name or ";" in name:
+            raise ValueError(f"非法 MySQL 标识符: {name!r}")
+        return f"`{name}`"
+
+    if db_type == "mysql":
+        ident_owner = _safe_mysql_ident(owner)
+        ident_tbl = _safe_mysql_ident(table_name)
+    else:
+        from web3.backend.core.db_adapter import quote_ident
+        ident_owner = quote_ident(owner, db_type)
+        ident_tbl = quote_ident(table_name, db_type)
     sql = f"SELECT COUNT(*) AS cnt FROM {ident_owner}.{ident_tbl}"
     try:
         row = db.fetchone(sql)