feat(boot+shell): add bootable disk image, unified scheduler and interactive user-space shell

- Implement Limine v8 boot protocol requests in dedicated PT_LOAD RW segment
- Configure IOPL=3 and SSE in arch setup for Ring 3 drivers and libc
- Unify scheduler context switching via switch_to and preempt_tick
- Support dual-source keyboard/serial input in sys_key_read
- Add automated 'make image' and 'make run' targets for instant QEMU launch
- Complete interactive UNIX-like shell (osh) with built-in commands & ramdisk

Makefile

@@ -18,11 +18,12 @@ LIB_DIR     := lib
 HAL_DIR     := hal
 SERVERS_DIR := servers
 KERNEL_DIR  := kernel
-ISO_DIR     := $(BUILD_DIR)/iso_root
+LIMINE_DIR  := boot/limine
 
 # Common Freestanding Flags
 COMMON_FLAGS := -Wall -Wextra -O2 -ffreestanding -fno-stack-protector \
                 -fno-pie -no-pie -mno-red-zone -m64 \
+                -mno-sse -mno-sse2 -mno-avx \
                 -I$(INCLUDE_DIR) -I$(LIB_DIR)/libc/include
 
 CFLAGS   := $(COMMON_FLAGS) -std=c11
@@ -35,18 +36,20 @@ INIT_SERVER  := $(BUILD_DIR)/init_server.elf
 UART_DRIVER  := $(BUILD_DIR)/uart_driver.elf
 SH_SERVER    := $(BUILD_DIR)/sh.elf
 PROCMGR      := $(BUILD_DIR)/procmgr.elf
+DISK_IMG     := $(BUILD_DIR)/opencoreC.img
 
 LIBC_OBJS    := $(BUILD_DIR)/string.o $(BUILD_DIR)/syscalls.o $(BUILD_DIR)/stdlib.o
 
-.PHONY: all kernel libc hal servers iso run clean help
+.PHONY: all kernel libc hal servers image run clean help limine-setup
 
 all: kernel libc hal servers
 	@mkdir -p $(BUILD_DIR)
 	@cp $(KERNEL_BIN) $(KERNEL_ELF)
 	@echo "======================================================="
-	@echo " [SUCCESS] opencoreC Skeleton Build Complete!"
+	@echo " [SUCCESS] opencoreC Build Complete!"
 	@echo " Kernel:   $(KERNEL_ELF)"
-	@echo " Servers:  $(INIT_SERVER), $(UART_DRIVER), $(SH_SERVER), $(PROCMGR)"
+	@echo " Servers:  $(INIT_SERVER), $(UART_DRIVER), $(SH_SERVER)"
+	@echo " Run:      make image && make run"
 	@echo "======================================================="
 
 kernel:
@@ -90,25 +93,60 @@ servers: libc hal
 	@$(LD) -T $(CONFIG_DIR)/user.ld -nostdlib -static -o $(PROCMGR) \
 		$(BUILD_DIR)/procmgr_main.o $(BUILD_DIR)/ipc.o $(LIBC_OBJS)
 
-# Staging Limine Boot ISO directory
-iso: all
-	@mkdir -p $(ISO_DIR)/boot $(ISO_DIR)/EFI/BOOT
-	@cp $(KERNEL_ELF) $(ISO_DIR)/boot/
-	@cp $(INIT_SERVER) $(ISO_DIR)/boot/
-	@cp $(UART_DRIVER) $(ISO_DIR)/boot/
-	@cp $(SH_SERVER) $(ISO_DIR)/boot/
-	@cp limine.conf $(ISO_DIR)/boot/limine.conf
-	@cp limine.cfg $(ISO_DIR)/boot/limine.cfg
-	@echo "[ISO] Staged boot files in $(ISO_DIR)/"
+# Download and build the Limine bootloader host tool
+limine-setup:
+	@if [ ! -d "$(LIMINE_DIR)" ]; then \
+		echo "[LIMINE] Cloning Limine v8 binary branch..."; \
+		git clone https://github.com/limine-bootloader/limine.git --branch=v8.x-binary --depth=1 $(LIMINE_DIR); \
+	fi
+	@echo "[LIMINE] Building host installer tool..."
+	@$(MAKE) -C $(LIMINE_DIR) limine
 
-run: all
-	@echo "[QEMU] Launching opencoreC in QEMU (SMP 4 Cores, Serial stdio)..."
-	@$(QEMU) -M q35 -smp 4 -m 512M \
-		-serial stdio \
-		-display none \
+# Build a 64 MiB bootable FAT32 disk image with Limine BIOS/UEFI
+image: all limine-setup
+	@echo "[IMAGE] Creating bootable disk image (64 MiB FAT32)..."
+	@dd if=/dev/zero of=$(DISK_IMG) bs=1M count=64 2>/dev/null
+	@parted -s $(DISK_IMG) mklabel msdos mkpart primary fat32 2048s 100% set 1 boot on 2>/dev/null
+	@mformat -F -i $(DISK_IMG)@@1M ::
+	@mmd -i $(DISK_IMG)@@1M ::/boot ::/EFI ::/EFI/BOOT
+	@# Kernel and userspace servers
+	@mcopy -i $(DISK_IMG)@@1M $(KERNEL_ELF)   ::/boot/
+	@mcopy -i $(DISK_IMG)@@1M $(INIT_SERVER)  ::/boot/
+	@mcopy -i $(DISK_IMG)@@1M $(UART_DRIVER)  ::/boot/
+	@mcopy -i $(DISK_IMG)@@1M $(SH_SERVER)    ::/boot/
+	@# Bootloader config
+	@mcopy -i $(DISK_IMG)@@1M limine.conf ::/
+	@mcopy -i $(DISK_IMG)@@1M limine.cfg  ::/
+	@mcopy -i $(DISK_IMG)@@1M limine.conf ::/boot/
+	@mcopy -i $(DISK_IMG)@@1M limine.cfg  ::/boot/
+	@# Limine bootloader files
+	@mcopy -i $(DISK_IMG)@@1M $(LIMINE_DIR)/limine-bios.sys ::/
+	@mcopy -i $(DISK_IMG)@@1M $(LIMINE_DIR)/limine-bios.sys ::/boot/
+	@mcopy -i $(DISK_IMG)@@1M $(LIMINE_DIR)/BOOTX64.EFI    ::/EFI/BOOT/
+	@# Install Limine Stage 1 into MBR
+	@$(LIMINE_DIR)/limine bios-install $(DISK_IMG) 2>&1 | grep -v "^Physical\|^Installing\|^Stage\|^Reminder"
+	@echo "[IMAGE] Done: $(DISK_IMG) (BIOS + UEFI bootable)"
+
+# Launch QEMU with serial terminal (keyboard works via -serial stdio)
+run: image
+	@echo "[QEMU] Launching opencoreC (SMP 4 cores, Serial terminal)..."
+	@echo "[QEMU] Type 'help' for commands. Ctrl+A X to exit QEMU."
+	@echo "-------------------------------------------------------"
+	@$(QEMU) \
+		-M q35 \
+		-smp 4 \
+		-m 512M \
+		-serial mon:stdio \
 		-no-reboot \
-		-no-shutdown \
-		-kernel $(KERNEL_ELF)
+		-display none \
+		-drive file=$(DISK_IMG),format=raw
+
+# Run without rebuilding image (faster iteration)
+qemu: $(DISK_IMG)
+	@echo "[QEMU] Quick launch from existing image..."
+	@echo "[QEMU] Type 'help'. Ctrl+A X to exit."
+	@$(QEMU) -M q35 -smp 4 -m 512M -serial mon:stdio -no-reboot -display none \
+		-drive file=$(DISK_IMG),format=raw
 
 clean:
 	@echo "[CLEAN] Removing build directory and cargo target..."
@@ -116,7 +154,16 @@ clean:
 
 help:
 	@echo "opencoreC Microkernel Build System"
+	@echo ""
 	@echo "Targets:"
-	@echo "  make all      - Build kernel, HAL, libc, and all user servers"
-	@echo "  make run      - Launch QEMU with SMP 4 Cores & Serial output"
-	@echo "  make clean    - Clean build artifacts"
+	@echo "  make all          - Build kernel, HAL, libc, and all user servers"
+	@echo "  make image        - Create bootable disk image (build/opencoreC.img)"
+	@echo "  make run          - Build image and launch in QEMU (interactive serial)"
+	@echo "  make qemu         - Quick relaunch without rebuild"
+	@echo "  make limine-setup - Download/build Limine bootloader"
+	@echo "  make clean        - Remove all build artifacts"
+	@echo ""
+	@echo "QEMU Controls:"
+	@echo "  Type commands in the terminal (serial I/O)"
+	@echo "  Ctrl+A then X  -> exit QEMU"
+	@echo "  Ctrl+A then C  -> QEMU monitor"