ifcviewer: wire FederatedFalseOrigin / ModelTransformation to viewport

Federation grows three granular signals so consumers can recompose only
what's affected:
  - configChanged()                        — federation unit changed
  - federatedFalseOriginChanged()          — stage 3 changed
  - modelTransformationChanged(fed_id)     — stage 4 changed for one model

Emitted from setConfig / setFederatedFalseOrigin / setModelTransformation
in addition to the existing dirtyChanged.

MainWindow gains applyFederatedFalseOriginToViewport and
applyModelTransformationToViewport helpers.  Each composes the matrix
from the current federation state (using composeFederatedFalseOrigin /
composeModelTransformation, which already exist on Federation.h) and
pushes to the viewport's setFederatedFalseOrigin /
setModelTransformation.  ModelTransformation reads ModelUnits and the
active CoordinateOperation matrix from SceneLoader::modelGeoref so
ModelLocal-frame `a` lifts correctly through stage 2 when authored.

Wiring:
  - federation.federatedFalseOriginChanged -> applyFederatedFalseOriginToViewport
  - federation.configChanged               -> stage 3 + walk all models for stage 4
  - federation.modelTransformationChanged  -> stage 4 for that one model
  - applyCoordinateOperationToViewport now also re-pushes stage 4 (the
    compose result depends on the active stage 2 when a_frame is ModelLocal)
  - openFederation() pushes the loaded FederatedFalseOrigin once load
    completes; per-model stage 4 falls out of the existing
    onLoadedFromStream / onDataSourceReady path.

End-to-end pipeline is now active under the AppSettings toggle: edit
the federation in memory and the viewport recomposes immediately.  UI
for editing (form-based dialog) still pending.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/ifcviewer-full/MainWindow.h

@@ -103,6 +103,16 @@ private:
     // or its IFC file isn't available (sidecar-hit before data-source
     // load); the call retries on onDataSourceReady.
     void applyCoordinateOperationToViewport(uint32_t mid);
+
+    // Push a model's ModelTransformation (stage 4) matrix to the viewport,
+    // composed from the federation's authoring intent + the model's units
+    // + the active CoordinateOperation matrix.  Identity when the model is
+    // not in the federation.
+    void applyModelTransformationToViewport(uint32_t mid);
+
+    // Push the federation-wide FederatedFalseOrigin (stage 3) matrix to
+    // the viewport.  Affects every loaded model.
+    void applyFederatedFalseOriginToViewport();
     QString formatElapsed(qint64 ms) const;
 
     ViewportWindow* viewport_ = nullptr;