capture: state the bounds tolerance as empirical, refuse unmeasurable renders, keep refused ones for diagnosis

The one-frame bound is not provable for a per-edge renderer; the test now shows where it breaks. Refused renders move out of the bank instead of being deleted, so the DAW experiment has something to read.

src/app/CMakeLists.txt

@@ -14,6 +14,7 @@ add_library(reaper_reasampler MODULE
     ${REASAMPLER_SRC_DIR}/shell/capture/scope_resolve.cpp
     ${REASAMPLER_SRC_DIR}/shell/capture/render_selection.cpp
     ${REASAMPLER_SRC_DIR}/shell/capture/render_isolation.cpp
+    ${REASAMPLER_SRC_DIR}/shell/capture/render_bounds_gate.cpp
     ${REASAMPLER_SRC_DIR}/shell/capture/realtime_lifecycle.cpp
     ${REASAMPLER_SRC_DIR}/shell/capture/capture_realtime_shell.cpp
     ${REASAMPLER_SRC_DIR}/shell/capture/capture_realtime_finalize.cpp