Function isNotNumber

isNotNumber<T>(u: T): u is RelaxedExclude<T, number>
Type guard that checks if a value is not a number.

Type Narrowing Behavior:
- Excludes number from the input type when true
- Preserves all other types in the union
Type Parameters
- T
  The type of the input value
Parameters
- u: T
  The value to check
Returns u is RelaxedExclude<T, number>
true if u is not a number, false otherwise. When true, TypeScript excludes number from the type.
Example
```
const mixed: unknown[] = [1, '2', 3];

const nonNumbers = mixed.filter(isNotNumber);

assert.deepStrictEqual(nonNumbers, ['2']);
```
- Defined in src/guard/is-type.mts:150