feat: built-in effect params, clip click-select, effect drag-and-drop, project load with plugins

- serializer resolves node types through the factory's dynamic
  (runtime-registered OpenFX) entries, so a project carrying plugin
  nodes loads again (was: "unknown node type"); covered by a new
  CI-gated round-trip test driving the real fixture plugin
- built-in effect nodes expose their inputs as inspector parameters
  like the C++ parameter editor: localized input names from the
  behavior, combo option tables via the new
  NodeBehavior::input_combo_strings (16 nodes, string-for-string from
  the C++ set_combo_box_strings), connection/data inputs excluded
- effect library: live drag-and-drop — onto the inspector's effect
  stack (lands at the indicator position) and onto the node editor
  canvas (creates the node at the drop point); double-click still
  appends to the selected clip
- inspector parameter controls are no longer recreated per render
  (gpui stack view caches them per effect), so sliders drag and
  checkboxes click; the view observes the engine and silently re-syncs
  values (undo/redo land on the widgets)
- timeline: left-press selects clips (plain/keep-multi/Ctrl-Cmd
  toggle); clip moves clamp the shared delta so no clip of a linked
  group lands before frame 0 instead of failing with "invalid move
  target"
- oakplugin: createInstance-rejected instances skip the destroyInstance
  notification (the plugin never owned them); vendor-suite fetchSuite
  misses moved behind OAK_OFX_TRACE; the worker logs the discovered/
  registered plugin counts
- CI: the OFX probe step also runs the serialization round-trip test
- gpui submodule: params view caching, clip click-select, library
  drag payload, graph_position_at

crates/oaknode/src/node.rs

@@ -501,6 +501,14 @@ pub trait NodeBehavior: Send {
 		}
 	}
 
+	/// The option labels of a combo input (C++ `set_combo_box_strings`,
+	/// called from each node's `retranslate`). Empty for non-combo inputs;
+	/// the default is no options.
+	fn input_combo_strings(&self, id: &str) -> Vec<&'static str> {
+		let _ = id;
+		Vec::new()
+	}
+
 	/// Inputs excluded from rendering (C++ `ignore_inputs_for_rendering()`).
 	fn ignore_inputs_for_rendering(&self) -> &[String] {
 		&[]