lightning:When importing non-enumerated values in Lightning, everything imports successfully without errors or prompts, and the inserted values are not the strings from the source file.

## Bug Report

When importing non-enumerated values in Lightning, everything imports successfully without errors or prompts, and the inserted values are not the strings from the source file.

### 1. Minimal reproduce step (Required)
1. create table a
```
CREATE TABLE `a` (
`id` bigint(20) NOT NULL AUTO_INCREMENT,
`mode` enum('aaa','bbb','ccc') NOT NULL,
PRIMARY KEY(`id`) CLUSTERED)
ENGINE = InnoDB DEFAULT CHARACTER SET = UTF8MB4 DEFAULT COLLATE = UTF8MB4_BIN AUTO_INCREMENT = 1284046222587412087
```

3. use lightning to load data from csv
[test.a.1.csv](https://github.com/user-attachments/files/17867474/test.a.1.csv)

lightning toml
```
[lightning]
level = "info"
check-requirements = false
status-addr = ':8289'
index-concurrency = 64
table-concurrency = 64
io-concurrency = 32
region-concurrency = 64

[tikv-importer]
backend = "local"
incremental-import = true
sorted-kv-dir = "/tiup/sort"
range-concurrency = 64

[tidb]
# Information of the target cluster
port = 4000
user = "root"
password = ""
host = "tidb-1-peer"
status-port = 10080
pd-addr = "pd-peer:2379"
build-stats-concurrency = 20
distsql-scan-concurrency = 15
index-serial-scan-concurrency = 20
checksum-table-concurrency = 2
[mydumper]
no-schema = true
data-source-dir = 'xxx'
[mydumper.csv]
header = false

[checkpoint]
# Whether to enable checkpoints.
enable = true
driver = "file"

[post-restore]
checksum = false
analyze = false

[conflict]
strategy = "replace"
```

### 2. What did you expect to see? (Required)
Lightning reports an error or prompts that the inserted value is not within the enumeration range.

### 3. What did you see instead (Required)
Lightning imports successfully, with no prompts or errors, and the inserted value is null."


### 4. What is your TiDB version? (Required)
v8.4.0