chore: organize repository build entry points and workflow docs

Makefile

@@ -1,10 +1,41 @@
-all: slime slime-cuda
+CXX ?= g++
+NVCC ?= nvcc
+CXXFLAGS ?= -O3 -std=c++17
+NVCCFLAGS ?= -O3 -std=c++17
 
+# Keep the original default build compatible; use `make bench` for the current CLI.
+.PHONY: all legacy bench research show tools test test-gpu clean help
+all: legacy
+legacy: slime slime-cuda
 slime: slime.cpp
-	g++ -o slime slime.cpp -O3 -std=c++17
-
+	$(CXX) $(CXXFLAGS) $< -o $@
 slime-cuda: slime.cu
-	nvcc -o slime-cuda slime.cu -O3 -std=c++17
-
+	$(NVCC) $(NVCCFLAGS) $< -o $@
+bench:
+	$(MAKE) -C bench
+research:
+	$(MAKE) -C research
+show:
+	$(MAKE) -C show
+tools:
+	$(MAKE) -C tools
+test:
+	$(MAKE) -C bench test
+test-gpu:
+	$(MAKE) -C bench test-gpu
 clean:
-	rm -f slime slime-cuda
+	rm -f slime slime-cuda sliming
+	$(MAKE) -C bench clean
+	$(MAKE) -C research clean
+	$(MAKE) -C codex clean
+	$(MAKE) -C show clean
+	$(MAKE) -C tools clean
+help:
+	@echo 'make bench        Build the current CUDA benchmark CLI'
+	@echo 'make test         Run CLI host-side checks (nvcc required, GPU not required)'
+	@echo 'make test-gpu     Run CLI GPU integration checks'
+	@echo 'make legacy       Build the original CPU/CUDA brute-force programs (default)'
+	@echo 'make research     Build research prototypes'
+	@echo 'make show         Build teaching examples'
+	@echo 'make tools        Build the single-chunk checker'
+	@echo 'make clean        Remove compiled outputs; retain reports and datasets'