docs(si-menu): improve and extend menu example

[robertwilde]

Closes #984

In the basic example, introduce 3 columns to trigger the menu, and simplify the menu.
Add a new "full-options" example, inline using the declarative API, and with a menu button click using the factory API.

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• I confirm that this MR follows the contribution guidelines.

[gemini-code-assist]

Code Review

This pull request improves the documentation for the si-menu component by simplifying the basic example and adding a new, more comprehensive "full options" example. The changes are well-structured and enhance the documentation. All identified areas for improvement, including a high-severity accessibility issue, code cleanup opportunities, and a suggestion to improve test code readability, remain valid as they do not contradict any provided rules.

[gemini-code-assist]

This icon-only button is missing an accessible name, which is an accessibility issue. Add an aria-label attribute to describe its purpose for screen reader users, for example aria-label="Options".

        [cdkMenuTriggerFor]="contextMenu"
        aria-label="Options"

[gemini-code-assist]

For better readability and maintainability, it's good practice to use more descriptive variable names for test examples instead of generic names like example1 and example2.

Suggested change

	const example1 = 'si-menu/si-menu-full-options';
	test(example1, async ({ page, si }) => {
	await si.visitExample(example1);
	await si.runVisualAndA11yTests();
	});
	const example2 = 'si-menu/si-menu-bar';
	test(example2, async ({ page, si }) => {
	await si.visitExample(example2);
	await page.getByText('Item 1').click();
	await si.runVisualAndA11yTests();
	});
	const fullOptionsExample = 'si-menu/si-menu-full-options';
	test(fullOptionsExample, async ({ page, si }) => {
	await si.visitExample(fullOptionsExample);
	await si.runVisualAndA11yTests();
	});
	const menuBarExample = 'si-menu/si-menu-bar';
	test(menuBarExample, async ({ page, si }) => {
	await si.visitExample(menuBarExample);
	await page.getByText('Item 1').click();
	await si.runVisualAndA11yTests();
	});

[gemini-code-assist]

This commented-out <ng-template> tag, along with its closing tag on line 36, appears to be a remnant from another example. Since this menu is displayed inline and not as a context menu, these comments are misleading and should be removed to improve clarity.

[gemini-code-assist]

The CdkContextMenuTrigger is imported but not used in the template si-menu-full-options.html. It can be removed from the imports array to keep the dependencies clean.

Suggested change

	imports: [SiMenuModule, CdkContextMenuTrigger, CdkMenuTrigger],
	imports: [SiMenuModule, CdkMenuTrigger],