Defer Design View's per-FX park to an idle tick; honest undo mask, compare-before-write, PreventUIRefresh bracket, O(1) handle resolve

src/app/CMakeLists.txt

@@ -38,6 +38,7 @@ add_library(reaper_reasampler MODULE
     ${LICE_SRC}
     ${REASAMPLER_SRC_DIR}/shell/capture/insert.cpp
     ${REASAMPLER_SRC_DIR}/shell/view/view.cpp
+    ${REASAMPLER_SRC_DIR}/shell/view/view_fx_park.cpp
     ${REASAMPLER_SRC_DIR}/shell/view/view_solo.cpp
     ${REASAMPLER_SRC_DIR}/shell/capture/track_guid.cpp
     ${REASAMPLER_SRC_DIR}/shell/capture/provenance_shell.cpp
@@ -59,6 +60,12 @@ target_link_libraries(reaper_reasampler PRIVATE json wire file_bytes bank_model
 # link graph free of the voice engine — a link edge to it here means the design drifted.
 target_include_directories(reaper_reasampler PRIVATE ${SDK_INC} ${WDL_INC})
 
+# The deferred FX-park queue's re-entrancy rule is pure (header-inline, no REAPER
+# types), so it is CTest-covered like a core/ module. Declared here rather than in a
+# src/shell/view/CMakeLists.txt because that directory deliberately has none — its
+# TUs are compiled into this target directly.
+reasampler_test(view_fx_park LINK fx_offline)
+
 # Bank-package import: the promptless verb plus its action skin. Kept as its own
 # appended block rather than merged into the lists above, so the two package
 # directions stay textually independent.