ifcviewer: move initWgpu + probeAndCreatePool + shutdown into ViewportCore (#84-l)

The instance/adapter/device/queue/pool/surface-format wgpu lifecycle now
lives in ViewportCore — including the OOM-scoped pool size probe and
the worker-thread startup. ViewportWindow::initWgpu becomes a Qt shell
that handles env-var tuning + nav-button preset wiring, then delegates
to core_.initWgpu(); the VW-only pipeline builders (HiZ, edge, overlays,
pick) still run after. ViewportWindow::shutdown drops the VW-only
resources (depth, msaa, hiz, edge, overlays, pick) and lets
core_.shutdown() release the shared wgpu handles it now owns.

The wgpu-native log callback (wgpuSetLogCallback / WGPULogLevel) is
gated on !__EMSCRIPTEN__: it's not part of the W3C spec header, and
the emdawnwebgpu port doesn't ship wgpu.h — validation errors there
land in the browser console regardless.

Drive-by: update test_federation to compare HomeView::target as
Eigen::Vector3f (left stale by #79 when QVector3D was retired).

src/ifcviewer/ViewportWindow.h

@@ -297,11 +297,6 @@ private:
     // candidate needs the space. Triggers requestUpdate() if more remain.
     void  driveStreamingLoads();
 
-    // Discover the largest single buffer wgpu will give us by descending
-    // from the device's limits.maxBufferSize through OOM error scopes.
-    // Allocates pool_ at the discovered size. Returns false only when
-    // even a tiny pool can't be created (i.e. the device is unusable).
-    bool  probeAndCreatePool();
     void  ensureDepthTexture(int w, int h);
     void  releaseDepthTexture();
     void  ensureMsaaColorTexture(int w, int h);