One undo-block opener for the whole tree: fourteen sites route through it, and the reclaim span can no longer swallow a user's act

The drain refuses a tick inside a foreign block; applyMode wakes the reclaimer
before it opens the span.

src/app/CMakeLists.txt

@@ -38,6 +38,7 @@ add_library(reaper_reasampler MODULE
     ${REASAMPLER_SRC_DIR}/shell/panel/draw_kit.cpp
     ${LICE_SRC}
     ${REASAMPLER_SRC_DIR}/shell/capture/insert.cpp
+    ${REASAMPLER_SRC_DIR}/shell/undo/undo_block.cpp
     ${REASAMPLER_SRC_DIR}/shell/view/view.cpp
     ${REASAMPLER_SRC_DIR}/shell/view/fx_reclaim.cpp
     ${REASAMPLER_SRC_DIR}/shell/view/view_lanes.cpp