refactor(input-date-picker, input-number, input-time-picker): wire up useForm

[jcfranco]

Related Issue: #8126

Summary

This PR refactors input-date-picker, input-number, and input-time-picker components' form association logic from the legacy form utilities to the useForm controller.

[Copilot]

Pull request overview

This PR migrates input-date-picker, input-number, and input-time-picker from the legacy hidden-input form utilities to the ElementInternals-based useForm controller as part of the broader form-associated refactor tracked in #8126.

Changes:

• Refactored form association logic in input-date-picker, input-number, and input-time-picker to use useForm (ElementInternals) and removed the legacy HiddenFormInputSlot/connectForm wiring.
• Updated Enter-key submission behavior to use formSupport.requestSubmit() when form-associated.
• Moved “form-associated” testing from Puppeteer e2e specs into Vitest browser e2e specs for the updated components.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
packages/components/src/components/input-time-picker/input-time-picker.tsx	Replaces legacy form utilities/hidden input slot with useForm controller integration.
packages/components/src/components/input-time-picker/input-time-picker.e2e.ts	Removes Puppeteer form-associated coverage for this component.
packages/components/src/components/input-time-picker/input-time-picker.browser.e2e.tsx	Adds browser-mode form-associated coverage for this component.
packages/components/src/components/input-number/input-number.tsx	Replaces legacy form utilities/hidden input slot with useForm controller integration.
packages/components/src/components/input-number/input-number.e2e.ts	Removes Puppeteer form-associated and hidden-input syncing coverage for this component.
packages/components/src/components/input-number/input-number.browser.e2e.tsx	Adds browser-mode form-associated coverage for this component.
packages/components/src/components/input-date-picker/input-date-picker.tsx	Replaces legacy form utilities/hidden input slot with useForm controller integration.
packages/components/src/components/input-date-picker/input-date-picker.e2e.ts	Removes Puppeteer form-associated coverage for this component.
packages/components/src/components/input-date-picker/input-date-picker.browser.e2e.tsx	Adds browser-mode form-associated coverage (single + range) for this component.

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[Copilot]

requestSubmit() will synchronously run constraint validation and typically focuses the first invalid control in the form. Because restoreInputFocus(true) runs immediately after requestSubmit(), it can steal focus back to the date-picker even when some other control is invalid, which is a behavioral change from the legacy submitForm() helper (it re-focused the invalid control on the next frame). Consider only restoring focus when the submission is actually valid/succeeds, or otherwise deferring/conditioning the focus restoration so it doesn't override the browser's invalid-control focusing behavior.

Suggested change

	this.formSupport.requestSubmit();
	this.restoreInputFocus(true);
	const form = (this.formSupport as { form?: HTMLFormElement | null }).form ?? null;
	const isValid = !form || form.checkValidity();
	this.formSupport.requestSubmit();
	if (isValid) {
	this.restoreInputFocus(true);
	}