feat(Switch): add Switch compound component

[johnleider]

Summary

• Add headless Switch compound component (Root, Group, Track, Thumb, HiddenInput, SelectAll) with dual-mode context (standalone boolean / group array)
• Add documentation page with examples (basic, group, indeterminate) and recipes
• Add JSDoc to all interfaces and barrel exports
• Create AppSwitch wrapper and refactor inline switch implementations in docs to use it

Test plan

• Verify standalone switch toggles on click and keyboard (Space/Enter)
• Verify group mode with array v-model selects/deselects values
• Verify SelectAll with indeterminate state (partial selection)
• Verify aria-checked, role="switch", and hidden input for form submission
• Verify docs page renders at /components/forms/switch
• Verify AppSwitch renders correctly in AppSettingsToggle and DashboardConsumer

[pkg-pr-new]

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commit: 3e59f9c