docs: record the CMake build-system split in COMPLETED; note the multi-config ctest flag

docs/COMPLETED.md

@@ -19,6 +19,32 @@ findings — all content cut that should have survived — and all ten were
 remediated and re-gated before merge. Driver: Daniel's instruction — *"Brief
 concise engineering comments. A little why, and maybe context, never WHAT."*
 
+### CMake build-system split (ad-hoc, Daniel's request)
+
+Split the 1423-line root `CMakeLists.txt` into a 91-line root plus 18 per-directory
+`CMakeLists.txt` files under `src/`, with two shared declaration helpers
+(`reasampler_pure_library`, `reasampler_test`) factored into a new
+`cmake/reasampler_targets.cmake`. The root now keeps only repo-global concerns:
+version/channel single-source-of-truth, `configure_file`, vendor path vars,
+`LICE_SRC`, `enable_testing()`, and the `add_subdirectory` calls. Comments throughout
+were rewritten to the project's comment conventions — phase/wave/ticket IDs removed,
+module semantics already owned by `src/**/CLAUDE.md` deleted, load-bearing build
+facts kept.
+
+Also fixed two duplicate-object-code defects surfaced by the split: 18 `core/`
+translation units were previously compiled directly into the `reaper_reasampler`
+module *while also* being linked in as static libraries — those 18 source entries
+were removed from the module's source list and 3 missing link edges
+(`view_tree`, `guid_diff`, `lane_keys`) added so every `core/` TU now enters through
+exactly one static-library link edge. A dead `bridge_marshal` link edge was also
+dropped from `reaper_reasampler`, and two inaccurate comments in
+`src/app/CMakeLists.txt` were corrected.
+
+No `.cpp`, `.h`, `tests/`, or `vendor/` file was touched. Behaviour is unchanged and
+was verified mechanically: same 130 targets, same 65 tests all passing,
+`reaper_reasampler.dll` byte-identical at 3,477,504 bytes, both channels
+(stable/beta) building to the same artifact names and locations as before.
+
 ### Θ-W1-T1 — zone-retirement
 
 ReaSampler 9000's zone-mapping system is retired: one loaded capture, one parameter