Refactor Studio GRIDV regression test module

CHANGELOG.md

@@ -1,3 +1,10 @@
+- 2026-08-25: Continued #2564 test-module refactoring by moving the contiguous
+  stable-selection GRIDV report/label regression family from
+  `test_studio_host_json_settings_page_layout_fields.cpp` into
+  `test_studio_host_json_settings_page_layout_grid_vertical_fields.inl`. The
+  aggregate test target, invocation order, Studio host JSON, report/label,
+  localization, and machine contracts are unchanged.
+
 - 2026-08-25: Continued #2564 test-module refactoring by moving the contiguous
   CDX/DCX/IDX/NDX/MDX index-probe and localized-diagnostic regressions from
   `test_vfp_assets.cpp` into `test_vfp_assets_index_probe_contracts.inl`. The

agent-handoff.md

@@ -1,5 +1,16 @@
 # Agent Handoff
 
+## V1 Studio GRIDV regression module
+
+The bounded #5230/#2564 structural slice moves the contiguous stable-selection
+GRIDV report/label regression family from
+`test_studio_host_json_settings_page_layout_fields.cpp` to
+`test_studio_host_json_settings_page_layout_grid_vertical_fields.inl`. The
+fragment remains in the same test translation-unit namespace; the aggregate
+executable, existing declarations, invocation order, fixtures, Studio host
+JSON, report/label, localization, and machine contracts remain unchanged. A
+focused native rerun is required before merge.
+
 ## V1 index-probe asset test module
 
 The bounded #5226/#2564 structural slice moves the contiguous CDX/DCX/IDX/NDX/