[LKasianAnsys]

Issue

Resolves #192

Summary

Client (WASM) mode now picks parts on the server instead of in the browser. This matches how geometry picking already works in client mode.

Backend
Added a pick_part_in_view trigger on LocalApp. It takes a pixel, the window size and the client's camera, and returns the node id under that pixel, or None. It doesn't change the selection.

• Added pick_part_in_view to VtkPipelineRenderer, which builds the pick view from the client's camera. VisorLocalScene calls it under the scene lock, and VisorVTKLocal wires it into LocalApp.
• Added a PickInViewPayload base class. PickPartInViewPayload and PickGeometryInViewPayload now extend it.

Frontend

• IRenderer has a new pickPartAsync(normX, normY). It replaces addViewerClickedListener with addCanvasClickListener, which reports a click's position and modifier keys but picks nothing.
• WasmRenderer sends pick_part_in_view to the server and parses the reply with a new PartPickReader. It no longer keeps its own actor-id to node-id map. The code that builds the pick view is now shared with pickGeometryAsync.
• VisorFrontend, VtkScene.js, ServerRenderer and NullRenderer are updated to the new click and pick flow.

Tests

• Python and Jest tests cover the new trigger, renderer, scene and click handling. Existing tests are adjusted to the new interfaces.