v0.27.3

Switch, Checkbox, and ProgressBar join Slider on the dual-channel
gesture path. on Toggled { ... } and on ValueChanged { ... } route
through dedicated handler components (SwitchHandler, CheckboxHandler,
ProgressBarHandler) instead of the generic GestureHandler.

Added

• SwitchEvent::Toggled { now } + SwitchHandler — fires after switch_handler flips Switch.on.
• CheckboxEvent::Toggled { now } + CheckboxHandler — fires after checkbox_handler flips Checkbox.checked.
• ProgressBarEvent::ValueChanged { new: f32, old: f32 } + ProgressBarHandler — fires when a Tap or DragMove moves ProgressBar.value (only when the new value differs from the old).
• ui! { Switch (...) on Toggled { ... } {} } and the same for Checkbox / ProgressBar — now, new, old auto-destructured into the body's scope. Qualified forms (on Switch::Toggled etc.) work too.
• gallery/examples/toggle_demo.rs — Switch + Checkbox in modifier-chain form with shared stats resource and live label.

Changed

• switch_handler, checkbox_handler, progress_bar_handler moved to View::with_internal_gesture. A user world.insert(entity, GestureHandler { ... }) on these components no longer overwrites the toggle / value-update behaviour.