fix(viewport): frame model-documentation drawing views correctly

A floating viewport with a real saved view — a non-zero view target, as a model
documentation drawing view or a detail/section viewport carries — now uses that
view directly instead of running the median-cluster overlap test. That test
measured against the densest sub-cluster (a big symbol library beside the small
view geometry) and wrongly auto-fit these viewports onto the library. A fully
uninitialised view (target AND centre both zero) frames its saved origin and
stays empty rather than auto-fitting the whole model in; the auto-fit rescue is
kept only for a stale target=(0,0,0) paired with a non-zero pre-georeference
centre.

Also widen the restored-view ortho depth half-range (view_height ×4 → ×64): a
thin projection such as a section/side view has content far deeper than its
visible height (its cut plane sits ~half an object-depth from the view target),
so the tighter range clipped the view outline behind the far plane. Orthographic
depth precision is linear, so the wider range costs no z-fighting.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/scene/camera_ops.rs

@@ -242,10 +242,15 @@ impl Scene {
             projection: view::camera::Projection::Orthographic,
             yaw,
             pitch,
-            // Sized from the saved view height rather than a zoom-scaled range,
-            // so a restored view keeps stable depth precision. `view_height` is
-            // the visible extent; a few multiples cover the drawing's depth.
-            depth_half_range: (view_height as f32 * 4.0).max(1.0),
+            // Sized from the saved view height (not a zoom-scaled range) so a
+            // restored view keeps stable depth precision. A THIN projection —
+            // e.g. a model-documentation section/side view whose cut plane sits
+            // half an object-depth from the view target — has content much
+            // deeper than its visible height, so the depth half-range must be a
+            // generous multiple: `×4` clipped a section view's outline that was
+            // ~6× the view height deep. Orthographic depth precision is linear,
+            // so the wide range costs no z-fighting.
+            depth_half_range: (view_height as f32 * 64.0).max(1.0),
         })
     }