## Description
- Add `isHeadless` field to `FrontComponent` entity so front components
can run without rendering UI in the command menu
- Introduce headless front component mounting logic:
`HeadlessFrontComponentMountRoot` at the application root,
`useMountHeadlessFrontComponent`, and `useUnmountHeadlessFrontComponent`
hooks to mount/unmount headless components
- Expand the SDK with new action components (`Action`, `ActionLink`,
`ActionOpenSidePanelPage`) and host communication functions
(`openSidePanelPage`, `unmountFrontComponent`)
- Move `CommandMenuPages` type to twenty-shared so the SDK can reference
it for side panel navigation
## Video QA
https://github.com/user-attachments/assets/4f9e3bb1-fcd1-42be-b3f4-a97e80c2add2
As part of the extensibility effort, we are introducing a new engine
entity called "Front Component". This represents a dynamic react
component that will be rendered in CommandMenu actions or in PageLayout
widgets
This PR introduce the entity and all the necessary boilerplate to make
it syncable and cachable in the engine
Raphaël Bosi