feat(view): mint managed lanes to separate cross-mode content per stance (D2 W3-A)

Pure planLaneMinting decides which tracks hold >1 mode's content and which managed
lane each item lands on; view.cpp applies it (I_FREEMODE/I_NUMFIXEDLANES/P_LANENAME/
I_FIXEDLANE) under one undo block, driven off the auto-tag detection tick. Manual lanes
and their items are never touched. Load-time reconcile rebuilds ownership from durable
lane names before reapplying active-mode visibility.

CMakeLists.txt

@@ -63,6 +63,10 @@ target_include_directories(mode_switch PUBLIC src)
 # ---------------------------------------------------------------------------
 add_library(view_mode_model STATIC src/view_mode_model.cpp)
 target_include_directories(view_mode_model PUBLIC src)
+# The pure lane-minting decision (planLaneMinting) names managed lanes via the ONE
+# durable-key convention in lane_keys (laneNameForMode), so the model depends on that
+# pure sibling. PUBLIC so every consumer (tests + module) resolves the symbol.
+target_link_libraries(view_mode_model PUBLIC lane_keys)
 
 # ---------------------------------------------------------------------------
 # 2d) Pure view_tree library — NO REAPER, NO SWELL. The one testable-outside-DAW