Add ControlPanel events Flow and sample subscription

[bartwell]

Motivation

• Deliver all Control Panel interactions as events so the host app can observe user actions and config changes centrally via a stream instead of only a single callback.
• Ensure events generated while the library UI overlays the app (e.g. activity paused on Android) are not lost and can be delivered when the app resumes.

Description

• Added a sealed class ControlPanelEvent with variants for module exit, save, value change and button click and placed it under module/.../data/ControlPanelEvent.kt.
• Introduced a buffered SharedFlow in ControlPanelActions and added emitEvent/emitButtonClick to publish events with replay and extra buffer capacity to tolerate temporary unavailability of subscribers.
• Exposed the events stream from ControlPanelAccessor as the event: Flow<ControlPanelEvent> property and kept the existing onButtonClick callback for compatibility.
• Emitted events from DefaultControlPanelComponent for module exit, save pressed, value changes and action button clicks, extended ControlPanelComponent with onActionButtonClick, and wired action buttons in ControlPanelContent through the component.
• Updated the sample app (sample/shared/App.kt) to collect Kick.controlPanel.event and log received events, and synchronized the stub module to the new API.

Testing

• No automated tests were run on the modified code.

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Codex Task