Feat: Overlap movie output and cut per-frame fast-mode work

- Gather the union of every movie frame's all-sky tiles once and read them in bounded batches, replacing the per-frame prefetch scan and log.
- Fuse the fast supersampled-buffer clear into the FFTW pack pass so a resolved frame starts clean with no serial memset.
- Split parallel HDR->RGB8 tone mapping from PNG encoding.
- Add a bounded single-producer/single-writer movie output queue used by both observer movies and multi-frame imported lens maps, with writer timing and error propagation.
- Add --png-compression-level and --movie-output-workers shared|reserve-one.
- Add --fast-fftw-plan estimate|measure|wisdom|wisdom-update with strict wisdom identity sidecars.
- Add staged movie timing, regression tests, and docs.

Makefile

@@ -117,6 +117,7 @@ CAMERA_TEST_TARGETS := $(TEST_OUT_DIR)/test_observer_minkowski $(TEST_OUT_DIR)/t
 FAST_PSF_FFTW_TEST_TARGET := $(TEST_OUT_DIR)/test_fast_psf_fftw
 FAST_PSF_FFTW_BENCH_TARGET := $(TEST_OUT_DIR)/benchmark_fast_psf_fftw
 TONE_MAP_TEST_TARGET := $(TEST_OUT_DIR)/test_tone_map
+MOVIE_OUTPUT_TEST_TARGET := $(TEST_OUT_DIR)/test_movie_output
 SENSOR_BLOOM_TEST_TARGET := $(TEST_OUT_DIR)/test_sensor_bloom
 SENSOR_BLOOM_BENCH_TARGET := $(TEST_OUT_DIR)/benchmark_sensor_bloom
 
@@ -232,6 +233,11 @@ $(FAST_PSF_FFTW_TEST_TARGET): tests/test_fast_psf_fftw.c $(CORE_MINKOWSKI_SOURCE
 $(TONE_MAP_TEST_TARGET): tests/test_tone_map.c src/optics.c src/optics.h $(CPU_FFTW_SOURCES) | $(TEST_OUT_DIR)
 	$(CC) $(CPPFLAGS) $(BUILD_CPPFLAGS) $(CFLAGS) $(BUILD_CFLAGS) $(OPENMP_FLAGS) -Isrc tests/test_tone_map.c src/optics.c $(CPU_FFTW_SOURCES) $(LDLIBS) -o $@
 
+# The movie-output queue links production optics + fast_psf_fftw only, so it
+# needs neither a catalog nor ray tracing.
+$(MOVIE_OUTPUT_TEST_TARGET): tests/test_movie_output.c src/movie_output.c src/movie_output.h src/optics.c src/optics.h $(CPU_FFTW_SOURCES) | $(TEST_OUT_DIR)
+	$(CC) $(CPPFLAGS) $(BUILD_CPPFLAGS) $(CFLAGS) $(BUILD_CFLAGS) $(OPENMP_FLAGS) -Isrc tests/test_movie_output.c src/movie_output.c src/optics.c $(CPU_FFTW_SOURCES) $(LDLIBS) -o $@
+
 $(FAST_PSF_FFTW_BENCH_TARGET): tests/benchmark_fast_psf_fftw.c $(CORE_MINKOWSKI_SOURCES) $(CPU_FFTW_SOURCES) | $(TEST_OUT_DIR)
 	$(CC) $(CPPFLAGS) $(BUILD_CPPFLAGS) $(CFLAGS) $(BUILD_CFLAGS) $(OPENMP_FLAGS) -Isrc $^ $(LDLIBS) -o $@
 
@@ -253,7 +259,7 @@ FAST_PSF_FFTW_TEST_DEP :=
 FAST_PSF_FFTW_TEST_RUN :=
 endif
 
-test: $(CAMERA_TEST_TARGETS) $(TEST_TARGET) $(FRAME_TEST_TARGET) $(SCHWARZSCHILD_TEST_TARGET) $(ALCUBIERRE_TEST_TARGET) $(OBSERVER_TRACK_TEST_TARGET) $(CATALOG_PREFETCH_TEST_TARGET) $(FAST_PSF_FFTW_TEST_DEP) $(TONE_MAP_TEST_TARGET) $(SENSOR_BLOOM_TEST_TARGET)
+test: $(CAMERA_TEST_TARGETS) $(TEST_TARGET) $(FRAME_TEST_TARGET) $(SCHWARZSCHILD_TEST_TARGET) $(ALCUBIERRE_TEST_TARGET) $(OBSERVER_TRACK_TEST_TARGET) $(CATALOG_PREFETCH_TEST_TARGET) $(FAST_PSF_FFTW_TEST_DEP) $(TONE_MAP_TEST_TARGET) $(MOVIE_OUTPUT_TEST_TARGET) $(SENSOR_BLOOM_TEST_TARGET)
 	$(TEST_OUT_DIR)/test_observer_minkowski
 	$(TEST_OUT_DIR)/test_observer_schwarzschild
 	$(TEST_TARGET)
@@ -264,6 +270,7 @@ test: $(CAMERA_TEST_TARGETS) $(TEST_TARGET) $(FRAME_TEST_TARGET) $(SCHWARZSCHILD
 	$(CATALOG_PREFETCH_TEST_TARGET)
 	$(FAST_PSF_FFTW_TEST_RUN)
 	$(TONE_MAP_TEST_TARGET)
+	$(MOVIE_OUTPUT_TEST_TARGET)
 	$(SENSOR_BLOOM_TEST_TARGET)
 	python3 tests/test_camera_cli.py $(BUILD_DIR) $(TEST_OUT_DIR)