chore: repo scaffold, READMEs (EN/pt-BR), version pins, source fetch+vendorize scripts

- pins OpenBSD 8.0 tarballs (sha256) and Linux 7.3.4 as the port targets
- scripts/fetch-sources.sh (C3SL primary, cdn fallback), scripts/vendorize.sh
- scripts/{kernel-config,build-kernel}.sh for the VM-lab kernel

Makefile

@@ -0,0 +1,31 @@
+# PF-on-Linux top-level make
+KERNELDIR ?= $(HOME)/lab/linux_kernel/linux-7.3.4
+
+.PHONY: module tools kernel test clean vm vm-destroy docs
+
+module:
+	$(MAKE) -C $(KERNELDIR) M=$(CURDIR)/module modules
+
+tools:
+	$(MAKE) -C tools KERNELDIR=$(KERNELDIR)
+
+kernel:
+	./scripts/build-kernel.sh
+
+vm:
+	./scripts/vm-create.sh
+
+vm-destroy:
+	./scripts/vm-destroy.sh
+
+test:
+	./scripts/vm-run-tests.sh
+
+docs:
+	@for f in docs/en/*.md; do echo "EN  $$f"; done
+	@for f in docs/pt-BR/*.md; do echo "PT  $$f"; done
+
+clean:
+	$(MAKE) -C $(KERNELDIR) M=$(CURDIR)/module clean || true
+	$(MAKE) -C tools clean || true
+	rm -rf out/