[LKasianAnsys]

Issue

Resolves #26

Context

This PR adds server-side rendering mode (RenderingMode.SERVER) streamed through trame-rca.

This adds a second way to render. The scene is rendered off-screen on the server, and the frames are streamed to the browser through trame-rca. The existing VTK-WASM path stays the default. Its mode is renamed from LOCAL to CLIENT so the two names read as a matching pair.

To avoid copying the 18 scene triggers into a second trame app, they move from LocalApp into a new shared base class, SceneTriggerApp. LocalApp and the new ServerApp both inherit from it.

Breaking change: RenderingMode.LOCAL / "local" is now RenderingMode.CLIENT / "client". The old name is not accepted any more. This affects the Python API, the REST InitProps.rendering_mode field and the CLI --rendering-mode option, though this was always the default and should have had no callers.

Changes

Rendering mode enum and defaults

• In core/visor_enums.py, RenderingMode now has two members: CLIENT (VTK-WASM in the browser) and SERVER (off-screen rendering streamed through trame-rca).
• The defaults in Visor, VisorVTK, api/server.py and api/models.py are now RenderingMode.CLIENT.
• The CLI help text now says the default is CLIENT. The outdated mention of HEADLESS is removed.
• VisorVTK.new sends SERVER to the new VisorVTKServer.

Shared trigger base: app/trame/scene_trigger_app.py (new)

• These moved out of local_app.py without changes: the SceneMutationApi protocol, the per-part payload models, the parse_payload decorator, and the lifecycle hooks, HTTP headers and www-path setup.
• The 18 shared triggers also moved: scene details, per-part state, variable range, camera sync, widget toggles, projection, cross-section plane and panel layout.
• A new abstract rendering_mode property is written to trame state under the key rendering_mode when the app is constructed. The client can read it to tell which mode it is in.
• LocalApp now subclasses SceneTriggerApp. It keeps only the triggers that exist only in client mode: pick_geometry and the two perf reports.

Server rendering pipeline (new)

• app/visor_vtk_server.py, VisorVTKServer: creates one ServerLoopBridge and one ServerStatePublisher, then the VisorServerScene and the ServerApp.
• vtk/scene/server_scene.py, VisorServerScene: Builds a ServerRenderer and a VisorRcaWindow, both using the scene's lock.
  • Streamed frames have no transparency, so the background is set to the client's theme color. These values match --visor-viewer-background in the client CSS.
  • Adds pick_part_at and set_dark_mode, both run under the scene lock.
  • push_runtime_state re-applies the background color after a state restore and requests a frame.
• app/trame/server_app.py, ServerApp:
  • Serves the shared triggers plus two that exist only in server mode: pick_part_at (render-window pixel → node id) and set_dark_theme.
  • Creates the trame-rca RemoteControlledArea ("view"). On on_server_ready, it builds the view handler (JPEG, 30 fps, quality 60 while interacting and 90 when still) and binds the bridge to it.
• app/trame/server_state_publisher.py, ServerStatePublisher:
  • Lets any thread write trame state; the actual write is scheduled on the trame event loop through AsyncRunner.
  • Publishes the camera record as server_camera_state, because a client watching a streamed view has no camera of its own to read.
  • The record is copied on the calling thread while the scene lock is held, so later camera changes can't alter what gets published.

Renderer / infrastructure

• ServerRenderer:
  • Its constructor now requires a CameraPublisher (a new protocol), and every camera write publishes the camera record after requesting a frame.
  • New set_background_rgb() changes the background color without requesting a frame.
• TrameServerManager exposes its async_runner.
• The docstrings in VisorSceneBase that described the old "RCA path" are updated to describe how the server path behaves now.

[ansBAkula]

Tested the LOCAL, sorry the CLIENT mode and no regressions observed for typical flows.

The base branch was changed.