feat: modernize Makefile

- Added `checkmake` to enforce good `Makefile` format.
- Added `help`, `test`, `lint-markdown`, `lint`, `clean`, and `all` targets.
- Added `install` target.
- Added target comments to streamline `help` command.

Makefile

@@ -1,12 +1,40 @@
-unit:
+.PHONY: all help install clean test-unit test-mutation test-fuzz test docs lint-go lint-makefile
+
+help: ## Show this help
+	@grep -E '^[a-zA-Z_-]+:.*##' $(MAKEFILE_LIST) | awk -F ':.*## ' '{printf "  %-15s %s\n", $$1, $$2}'
+
+install: ## Install dev tools
+	go install github.com/golangci/golangci-lint/cmd/golangci-lint@latest
+	go install github.com/checkmake/checkmake/cmd/checkmake@latest
+	go install github.com/go-gremlins/gremlins/cmd/gremlins@latest
+	go install golang.org/x/tools/cmd/godoc@latest
+	go install golang.org/x/vuln/cmd/govulncheck@latest
+
+test-unit: ## Run unit tests with coverage
 	go test ./... -cover -v
 
-mutation:
+test-mutation: ## Run mutation tests with gremlins
 	gremlins unleash
 
-fuzz:
-	go test ./... -fuzz=$(FN)
+test-fuzz: ## Run all fuzz tests for 30s each
+	@for func in $$(grep -r --include='*_test.go' -oh 'func Fuzz\w*' . | sed 's/func //'); do \
+		echo "Fuzzing $$func..."; \
+		go test ./... -fuzz="^$$func$$" -fuzztime=30s; \
+	done
 
-docs:
+test: test-unit test-mutation test-fuzz ## Run all tests
+
+lint-go: ## Lint Go code
+	golangci-lint run ./...
+
+lint-makefile: ## Lint the Makefile
+	checkmake Makefile
+
+docs: ## Serve godoc locally
 	@echo ">>> Visit: http://localhost:6060/pkg/git.maximhutz.com/tools/dsa/"
-	godoc -http=:6060
+	godoc -http=:6060
+
+clean: ## Clean build and test caches
+	go clean -cache -testcache
+
+all: lint-go lint-makefile test ## Run all checks and tests