wgpu: bonsai-ready API surface + direct-IFC ingestion + streaming-always

Make the wgpu viewport ready for bonsai's verb actions, federation
refresh, and tool routing — i.e. callable from an outside host, not
just from the minimal viewer's own hotkeys.

Surface additions on WgpuViewportWindow:
- Qt signals: objectPicked, frameStatsUpdated, surfacePickedInTool,
  toolModeChanged, toolBackspacePressed.
- FrameStats struct + rolling 60-sample frame-time window for the
  fps field; emit at end of render() so external listeners see fresh
  numbers in the same tick.
- InstanceLookup struct + findInstance(object_id, ...) const for the
  measurement tools' O(1) object → (model, mesh, placement) resolve.
- Federation hooks (setFederatedFalseOrigin / setModelCoordinateOperation
  / setModelTransformation) + per-model coordinate_operation_meters /
  model_transformation_meters fields on WgpuModelGpuData. Implement
  composeInstanceFromPlacement + recomposeAndUploadModel so each setter
  actually applies — model recompose runs in double, casts to float for
  the GPU upload, and refreshes per-chunk world AABBs. meshLocalToGlobal
  now composes coordinate_operation · placement properly.
- showModel / hideModel for per-model visibility, plus element-level
  verbs (hideSelectedElements / isolateSelectedElements / showAllElements
  / invertElementVisibility) and setSelectedObjectId / cameraState() /
  projectionOrtho() / toggle{Area,Length,Volume}Tool wrappers.
- Section-cutting methods (toggleSectionTool / clearSectionPlanes /
  sectionToolActive) moved to public so bonsai's Commands.cpp can call.
- QVector3D overload of computeObjectAabb to match the GL signature.
- ToolMode::None → ToolMode::NoTool (X11 macro collision avoidance).

Direct-IFC ingestion (A-path), mirrors the GL streaming push API:
- uploadMeshChunk / uploadInstanceChunk stage into pending_direct_loads_
  using the same vertex quantisation as SidecarBuilder so direct-load
  and sidecar-load produce byte-identical buffers.
- finalizeModel wraps the staged data in a file-less StreamingSidecar,
  routes through the existing applyCachedModel chunk planner, then
  gathers per-chunk vertex+index bytes from memory and feeds
  applyStreamedChunk synchronously. Every chunk lands is_resident=true
  immediately (no disk I/O to defer).

Streaming collapse:
- Delete the applyCachedModel(SidecarData) full-load path entirely.
- Rename applyCachedModelStreaming → applyCachedModel; loadSidecar
  always uses the metadata-only reader. Drop the --streaming CLI flag
  from IfcViewerWgpuMinimal and the streaming_enabled_ field.

WgpuSelectionState::ids() → selectionIds() so bonsai's
`viewport_->selection().selectionIds()` compiles unchanged.

Eigen3 added as a public dep of IfcViewerWgpu for the federation
matrices.

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

src/ifcviewer-wgpu/WgpuModelGpuData.h

@@ -22,6 +22,8 @@
 
 #include <webgpu/webgpu.h>
 
+#include <Eigen/Dense>
+
 #include <cstddef>
 #include <cstdint>
 #include <limits>
@@ -341,6 +343,15 @@ struct WgpuModelGpuData {
     // is gone; cull iterates m.chunks instead.
 
     bool hidden = false;
+
+    // Per-model federation matrices in metres. Default identity → no
+    // per-model contribution to the composed transform. See bonsai's
+    // Federation.h for the full pipeline composition order. Stored
+    // here so setModelCoordinateOperation / setModelTransformation
+    // have somewhere to land; the recompose-and-reupload pass that
+    // would actually apply them is deferred.
+    Eigen::Matrix4d coordinate_operation_meters = Eigen::Matrix4d::Identity();
+    Eigen::Matrix4d model_transformation_meters = Eigen::Matrix4d::Identity();
 };
 
 // Release every wgpu handle in `m` (including per-chunk and per-model pool