Preserve authored projection content and contextual canvas selection

docs/language.rst

@@ -409,8 +409,12 @@ filters rather than widening them to All.
 
 Traceability views retain their established two-layer projection: default options
 preserve eligible OA and SA lines. Their hidden-edge, category and context
-references may therefore select either layer. All ordinary projections require
-these references in the declared diagram layer. A filter never hides the other
+references may therefore select either layer. Ordinary string projections retain
+these references from either layer as saved presentation choices; they still
+render only their declared layer. Switching projections MUST preserve those
+choices, including explicit empty selections. Existing-object, reference-kind,
+family and uniqueness constraints still apply. Typed StateMachine and Scenario
+views retain layer-scoped reference admission. A filter never hides the other
 layer merely because the Traceability diagram has an OA or SA layer label.
 
 Versions 1–5 reject the new relation, category constructor, diagram field (even
@@ -1073,6 +1077,20 @@ capabilities with their involvement, exploitation, include, extend and
 generalization links. Decomposition and Overview retain general containment;
 Overview also exposes all relationships. These string projections hide
 inapplicable placements without deleting them or changing semantic records.
+This includes opposite-layer placements retained after leaving Traceability.
+Changing between string projections changes only the projection value; placement
+identities, positions, sizes, collapsed state, port anchors, routes and visibility
+choices remain authored. Returning to Traceability restores their applicability.
+Ordinary views MUST NOT render opposite-layer nodes, parents, ports or lines.
+This current-version admission correction does not broaden frozen source/JSON
+versions 1–6: their layer-scoped placement and visibility checks remain required
+before migration. Earlier version-7 implementations can reject ordinary views
+containing these retained opposite-layer records.
+
+The explicit RelocateNode operation moves a placement to a different diagram
+only when its element belongs to the destination layer or the destination is
+Traceability. Retaining an existing hidden placement through a projection change
+does not authorize a relocation that immediately hides it in another layer.
 
 A StateMachine projection MUST reference an existing StateMachine in the
 diagram's layer. Its placements MUST refer to that machine, its Regions, or