Use modern null handling

Leverage modern JavaScript operators and patterns for cleaner, more robust null and undefined handling. This improves code readability and reduces boilerplate while maintaining safety.

Key patterns to adopt:

1. Nullish coalescing (??) for default values when you specifically want to handle null and undefined:

   // Instead of
   return this.args.onChange ? this.args.onChange : () => {};
   // Use
   return this.args.onChange ?? (() => {});
   

2. Nullish coalescing assignment (??=) for lazy initialization:

   // Instead of
   if (!this.#pendingCleanup[phase]) {
     this.#pendingCleanup[phase] = [];
   }
   // Use
   this.#pendingCleanup[phase] ??= [];
   

3. Logical OR assignment (||=) for falsy value defaults:

   // Instead of
   value = value || "";
   // Use
   value ||= "";
   

4. Leverage truthy/falsy behavior to simplify boolean checks: ```javascript // Instead of return d.hours() !== 0 || d.minutes() !== 0 || d.seconds() !== 0; // Use return d.hours() || d.minutes() || d.seconds();

// Instead of .filter((e) => e) // Use .filter(Boolean)

5. **Avoid redundant null checks** when functions handle undefined gracefully:
```javascript
// Instead of
if (this.handleBlurTimer) {
  cancel(this.handleBlurTimer);
}
// Use (since cancel handles undefined)
cancel(this.handleBlurTimer);

These patterns reduce code verbosity while maintaining or improving null safety, and they clearly express intent about how null/undefined values should be handled.