Enforced kernel and userland version sync (#65)

Summary:
This change makes the ThunderOS userland build use the kernel's recorded
version metadata and fail fast when the generated userland header drifts
from the kernel VERSION.

Changes:
- Generated `external/userland/build/generated/thunderos_version.h` from
the ThunderOS `VERSION` file during `make userland`
- Added a clean fallback when `VERSION_CODENAME` is absent
- Added `make check-abi-version` and ran it automatically after the
userland build
- Kept the userland banner/version header aligned with the kernel
version that ships with it

Testing:
- `bash -n build_userland.sh`
- `git diff --check`
- `make userland`
- `make check-abi-version`

Author: byteshiftlabs

Makefile

@@ -118,7 +118,7 @@ DOCKER_USER ?= $(shell id -u):$(shell id -g)
 FS_IMG := $(BUILD_DIR)/fs.img
 FS_SIZE := 10M
 
-.PHONY: all clean run debug fs userland test test-quick help docker-build-env docker-verify docker-shell
+.PHONY: all clean run debug fs userland check-abi-version test test-quick help docker-build-env docker-verify docker-shell
 
 # Default target - must be first
 all: $(KERNEL_ELF) $(KERNEL_BIN)
@@ -292,9 +292,22 @@ userland:
 	@echo "$(BOLD)$(BLUE)━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━$(RESET)"
 	@chmod +x build_userland.sh
 	@./build_userland.sh
+	@$(MAKE) --no-print-directory check-abi-version
 	@echo "$(BOLD)$(BLUE)━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━$(RESET)"
 	@echo ""
 
+check-abi-version:
+	@kernel_ver=$$(tr -d '\n' < VERSION); \
+	userland_ver=$$(sed -n 's/^#define THUNDEROS_VERSION_STRING "\(.*\)"/\1/p' external/userland/build/generated/thunderos_version.h 2>/dev/null || echo 'MISSING'); \
+	if [ "$$kernel_ver" != "$$userland_ver" ]; then \
+		echo "$(RED)✗ ABI version mismatch:$(RESET) kernel=$$kernel_ver userland=$$userland_ver"; \
+		echo "  The userland was built against a different kernel version."; \
+		echo "  Run 'make userland' to rebuild with the current kernel version."; \
+		exit 1; \
+	else \
+		echo "$(GREEN)✓ ABI version match:$(RESET) kernel=$$kernel_ver userland=$$userland_ver"; \
+	fi
+
 test:
 	@cd tests/scripts && bash test_runner.sh
 

build_userland.sh

@@ -10,8 +10,10 @@ readonly OBJCOPY="${CROSS_COMPILE}objcopy"
 
 readonly USERLAND_DIR="$(cd "$(dirname "$0")" && pwd)/external/userland"
 readonly BUILD_DIR="${USERLAND_DIR}/build"
+readonly REPO_ROOT="$(cd "$(dirname "$0")" && pwd)"
+readonly GENERATED_DIR="${USERLAND_DIR}/build/generated"
 
-readonly CFLAGS="-march=rv64gc -mabi=lp64d -nostdlib -nostartfiles -ffreestanding -fno-common -O0 -g -Wall"
+readonly CFLAGS="-march=rv64gc -mabi=lp64d -nostdlib -nostartfiles -ffreestanding -fno-common -O0 -g -Wall -I${GENERATED_DIR}"
 readonly LDFLAGS="-nostdlib -static"
 readonly LDSCRIPT="${USERLAND_DIR}/lib/user.ld"
 
@@ -83,6 +85,28 @@ build_program() {
 
 # Create build directory
 mkdir -p "${BUILD_DIR}"
+mkdir -p "${GENERATED_DIR}"
+
+# Generate version header from the kernel VERSION file so userland
+# binaries always report the same version as the kernel they ship with.
+kernel_version="$(tr -d '\n' < "${REPO_ROOT}/VERSION")"
+if [[ -f "${REPO_ROOT}/VERSION_CODENAME" ]]; then
+    kernel_codename="$(tr -d '\n' < "${REPO_ROOT}/VERSION_CODENAME")"
+else
+    kernel_codename="ThunderOS"
+fi
+cat > "${GENERATED_DIR}/thunderos_version.h" <<VEOF
+#ifndef THUNDEROS_VERSION_METADATA_H
+#define THUNDEROS_VERSION_METADATA_H
+
+#define THUNDEROS_VERSION_STRING "${kernel_version}"
+#define THUNDEROS_VERSION_TAG "v${kernel_version}"
+#define THUNDEROS_VERSION_CODENAME "${kernel_codename}"
+#define THUNDEROS_RELEASE_LABEL "v${kernel_version} ${kernel_codename}"
+
+#endif
+VEOF
+echo -e "${GREEN}✓${NC} Version header: v${kernel_version} (${kernel_codename})"
 
 print_header