Function isRecord

isRecord(u: unknown): u is UnknownRecord
Type guard that checks if a value is a plain object (record) - a non-null object that is not an array.

This function is useful for identifying "plain" JavaScript objects (also called records or dictionaries) - objects that are typically used as key-value collections. It excludes arrays, functions, and special object types like Date, RegExp, etc., focusing on objects that can be safely treated as property collections.

Type Narrowing Behavior:
- Narrows unknown to UnknownRecord (equivalent to Record<PropertyKey, unknown>)
- Excludes null, undefined, primitives, arrays, and functions
- Returns true for plain objects {}, object literals, and objects created with Object.create()
- Returns false for arrays, even though they are technically objects
Implementation: Uses isNonNullObject() to check for objects, then Array.isArray() to exclude arrays.
Parameters
- u: unknown
  The value to check
Returns u is UnknownRecord
true if u is a non-null object and not an array, false otherwise. When true, TypeScript narrows the type to UnknownRecord.
Example
```
const entries: unknown[] = [{ id: 1 }, ['tuple']];

const records = entries.filter(isRecord);

assert.deepStrictEqual(records, [{ id: 1 }]);
```
See
- isNonNullObject - For checking any object type (includes arrays)
- hasKey - For checking if a record has specific keys
- Defined in src/guard/is-record.mts:41