wip: deblock smoke test

CMakeLists.txt

@@ -136,6 +136,21 @@ add_test(NAME idct_bitexact_cpu COMMAND test_idct_bitexact 320 240
 # gets slow we'll split into a CTest LABEL for opt-in.
 add_test(NAME idct_bitexact_1080p COMMAND test_idct_bitexact 1920 1088)
 
+# ---- Stage 2 PR-b deblock smoke ------------------------------------
+#
+# Validates flush_frame's per-frame deblock dispatch (luma + chroma,
+# V + H, bS<4 + bS=4 intra — up to 8 dispatches added after IDCT).
+# Strategy: same input through substrate=CPU and substrate=QPU, assert
+# byte-exact match (transitive bit-exact gate — daedalus-fourier's own
+# test_api_h264 already validates each substrate against a C reference,
+# so CPU-QPU equivalence here means both match the spec).  Plus an
+# anti-no-op check: run a third pass with edges removed and assert
+# different output, proving deblock actually ran.
+add_executable(test_deblock_smoke tests/test_deblock_smoke.c)
+target_link_libraries(test_deblock_smoke PRIVATE daedalus_decoder)
+target_compile_options(test_deblock_smoke PRIVATE -O2)
+add_test(NAME deblock_smoke COMMAND test_deblock_smoke)
+
 # ---- Benchmarks (not gated by ctest) ------------------------------
 #
 # Build-time only; user runs them by hand when checking perf.  Adding