Record viewport associations for new dimensions

Removes PR3's `viewport_frame` seam in `viewport_ref.rs`; the frame is
PR1's camera-derived one everywhere.

The five dimension commands (DIMLINEAR / DIMALIGNED / DIMRADIUS /
DIMDIAMETER / DIMANGULAR) now record a real association when they
measure through a viewport. The commit path's one association gate
(`dimension_association_allowed`, added when PR2 was stacked) gains an
else-branch: where PR2 committed the dimension unassociated and PR1's
inference guard returned an empty source list, `Scene::attach_viewport_
dimension_association` now stores the whole chain — dimension ->
viewport -> block path -> entity -> feature — from the AcceptedSnaps PR1
captured, in definition-point slot order.

* `Scene::dimension_association_slot_points` names that order, including
  the radial dimensions `dimension_reference_points` does not cover.
* `OpenCADStudio::viewport_dimension_snaps` builds the slot array. A snap
  whose paper point is no longer the definition point it fills has its
  model point recomputed from that definition point through the frame:
  the object pick records one click for both extension origins, and a
  rotated DIMLINEAR projects its origins onto the measuring axis.
* Radial dimensions take their own path inside
  `attach_viewport_dimension_association`. Their single reference is an
  osnap type 10 carrying the radial marker (which circle / which polyline
  arc segment) and the angle around it; `source_reference` would hand
  back the generic curve-parameter marker -2, which
  `radial_source_for_marker` cannot find.

One measurement rule, documented in `viewport_ref::measurement_rule`:
`actual_measurement` is always the RAW measurement in the dimension's own
space (paper, for a viewport dimension), and the viewport compensation
lives only in the magnitude of the negative DIMLFAC override, applied
once by the formatter. PR2's persistence already followed it; PR3's
refresh did not — it substituted the model distance times
`model_factor()`, which made a refreshed dimension read `user_lfac` times
too much versus an identical freshly-created one. Refresh now writes the
paper measurement (a debug assert pins resolved paper points to the model
points through the frame), and `axis_distance` goes with it.

Block sub-entity snaps: verified that `block_cache` stamps the top-level
INSERT's handle onto every expanded and clipped sub-wire, so
`wire_source` can only ever report the INSERT — nested inserts included.
`OpenCADStudio::resolve_source_block_path` now descends from that INSERT
at accept time (using the object-pick path's existing
`resolve_measurable_entity`, so arbitrary depth, not just one level) and
fills `SnapSourceRef.block_path` with the real inner entity. Where the
descent cannot identify one — a non-planar-pickable type such as text,
hatch, spline or solid, or nesting past eight levels — the source stays
the INSERT with an empty path, which is coarser but never wrong. Both the
limitation and where it bites are documented on
`Scene::resolve_block_snap_source` and `SnapResult::source`.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

src/app/command_driver.rs

@@ -376,7 +376,7 @@ impl OpenCADStudio {
             // accepted-snap list must stay index-parallel with the points the
             // command collects (PR1). Interactive picks record themselves in
             // the click handler and never reach here.
-            self.record_accepted_snap(None, None, *point);
+            self.record_accepted_snap(i, None, None, *point);
         }
         if default_start {
             let StepInput::Point(point) = &input else {
@@ -2220,6 +2220,14 @@ impl OpenCADStudio {
                             changes.sort_by_key(|(handle, _)| handle.value());
                             changes.dedup_by_key(|(handle, _)| handle.value());
                             self.tabs[i].scene.bump_entities(&changes);
+                        } else if association_mode == 2 {
+                            // Measured through a layout viewport: a paper-space
+                            // association would bind projected coordinates to
+                            // geometry that is not on the sheet. Record the real
+                            // chain instead — dimension -> viewport -> block
+                            // path -> entity -> feature — from the AcceptedSnaps
+                            // PR1 captured, in definition-point slot order.
+                            self.attach_viewport_dimension_association(i, handle);
                         }
                     }
                     pending