Logical Bug in `NOT ( ... XOR ... )` Evaluation with Implicit Type Conversion

Summary
There appears to be a logical bug where `NOT (expr1 XOR expr2)` is not the boolean complement of `(expr1 XOR expr2)` under implicit type conversion (numeric/text values).
This violates core boolean consistency: rows can satisfy both `P` and `NOT P`, or satisfy neither, for the same predicate `P`.

Environment

• Deployment: Docker container (`mariadb:12.2.2`)
• Connection used: `mysql -h 127.0.0.1 -P 23306 -u root -proot`
• `sql_mode`:
• `STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION`

Reproducibility

• Reproduced consistently in the environment above.
• Also observed in others independent generated workloads (same bug pattern):
• `3 vs 4`
• `21 vs 0`
• `4 vs 1`
• `1 vs 0`

Minimal Reproducer (Constants)
```sql
SELECT
0.1 XOR 2 AS p,
NOT (0.1 XOR 2) AS not_p,
(0.1 XOR 2) IS NULL AS p_is_null;
```

Expected

• `p = 1`
• `not_p = 0`
• `p_is_null = 0`

Actual

• `p = 1`
• `not_p = 1`
• `p_is_null = 0`

`NOT p` is not complementing `p`.

Logical Consistency Reproducer (Row Count Mismatch)

DROP DATABASE IF EXISTS bug_logic_xor;

CREATE DATABASE bug_logic_xor;

USE bug_logic_xor;

CREATE TABLE t(v DOUBLE);

INSERT INTO t VALUES (0.1), (2), (NULL);

-- Baseline row count

SELECT COUNT(*) AS baseline FROM t;

-- Logical decomposition by P / NOT P / P IS NULL

SELECT COUNT(*) AS decomposed_cardinality

FROM (

  SELECT v FROM t WHERE (v XOR 2)

  UNION ALL

  SELECT v FROM t WHERE NOT (v XOR 2)

  UNION ALL

  SELECT v FROM t WHERE (v XOR 2) IS NULL

) q;

-- Row-level evidence

SELECT

  v,

  (v XOR 2) AS p,

  NOT (v XOR 2) AS not_p,

  ((v XOR 2) IS NULL) AS p_is_null

FROM t;

Expected

• `baseline = decomposed_cardinality = 3`
• For each non-NULL row, exactly one of `p` or `not_p` is true.

Actual

• `baseline = 3`
• `decomposed_cardinality = 4`
• Row-level output includes `p=1` and `not_p=1` for `v=0.1` (overlap).