Introduce scene node definitions for rendering and hits

[kostyafarber]

Summary

This PR starts moving scene behavior behind node definitions instead of hard-coding glyphs in editor/rendering paths.

• Adds NodeDefinition registration and moves glyph pointer hit-testing into GlyphNodeDefinition.
• Adds RenderContext so renderer-owned resources, including the marker layer, flow through frame dispatch instead of being retained by scene-layer helpers.
• Adds marker frame begin/commit lifecycle so stale marker draws are cleared by the renderer pipeline.
• Renames root canvas drawing setup from glyph space to scene space.
• Moves glyph outline, debug, segment, control-line, handle, and anchor rendering into GlyphNodeDefinition.
• Makes NodeObject.bounds() forward to the registered node definition.

Why

Text, image, and plugin-defined nodes should not require editing SceneLayer, BackgroundLayer, or Editor.getPointerTarget for basic draw/hit behavior. This keeps render pass ordering in the renderer while letting node kinds own their content and internal chrome.

Follow-up

Marker placement still has one asymmetry: CPU handle drawing inherits placement from the canvas transform stack, while GPU marker drawing receives the glyph node offset through Handles.draw(ctx, node, ...). The intended follow-up is a marker transform/offset capability so canvas and marker placement share the same transform discipline before issue #129 lands node transforms.

Validation

• pnpm format:check
• pnpm lint:check
• pnpm typecheck
• pnpm build:native:debug && pnpm --filter @shift/desktop test
• Manual smoke test in the app: open glyph, render glyph/chrome, and interact with hover/selection/drag paths.