Focus boundary SG tree example

This app validates FocusBoundary focus enter and leave behavior when a TypeScript focus panel is inside a mixed BrightScript and TypeScript SceneGraph tree.

Purpose

Unlike the pure TypeScript focus-boundary examples, this app uses a BrightScript scene (MixedFocusScene) that owns the tree and hands key events and focus activation to a TypeScript anchor node (TsMiddlePanel, extending FocusBoundaryBase). The example shows that the TypeScript-driven focus model integrates with native SceneGraph focus: focus enters and leaves the TypeScript panel, and key events that the panel does not handle bubble back to BrightScript.

Summary

This example covers the following behaviors:

BrightScript and TypeScript focus handoff through the keyEvent and focusActive inputs and the handledKeys and focusPath outputs
A flat 2×2 grid (navigationMap, without nesting) beside nested FocusBoundary components (Sidebar and Content)
rememberLastFocus and onFocusGained and onFocusLost cascades across nested boundaries
Edge keys (up and down) left unclaimed so they bubble to BrightScript for navigation between components
The setFocusPath function of RootFocusBoundary, which reports the active focus path

Development

To build, test, and lint the example, run these commands:

npx rk dev          # Build + deploy to Roku device
pnpm test           # Run tests
pnpm run lint       # Lint sources