feat: proper IPC-based boot — init loads servers from storage via IPC, VirtIO GPU driver

Complete microkernel boot pipeline: adapter loads only init + storage + display
from disk. Init bootstraps all other servers by reading binaries from the
storage server via IPC, parsing ELF, creating processes, mapping pages, and
spawning threads.

New syscalls:
- CreateEndpoint: userspace endpoint creation with full capability grant
- DebugPutchar: debug output to UART from userspace
- MapPage: cross-process page mapping (init loads binaries into children)
- SpawnThreadIn: spawn thread in another process via capability

Key fixes:
- Per-process L1 page tables for VPN[2]=0 (prevents cross-process corruption)
- Separate kernel_pt from page_tables[0] (init pid=0 overwrote kernel PT ref)
- Thread Running state set in switch_to_next (syscalls rejected without it)
- Pending IPC results applied during context switch
- SIE disabled during boot (timer can't preempt into unready processes)
- User heap VA starts at 0x40000 (avoids shared buffer at 0x30000)
- RequestPages maps at user VAs via per-process heap allocator

VirtIO GPU:
- Adapter probes for GPU device, initializes resource/scanout/backing
- Display server writes to mapped framebuffer, flushes via GPU virtqueue
- 640x480 BGRA framebuffer with transfer-to-host and resource-flush

Storage server:
- Userspace VirtIO block driver using pre-mapped MMIO and DMA pages
- FAT16 filesystem reader serving file-read requests via IPC
- Shared buffer protocol: init writes filename, storage writes file data

Echo app for IPC testing (adapter-loaded echo proved the pipeline end-to-end).

scripts/make-disk-image.sh

@@ -8,43 +8,30 @@ BUILD_DIR="target/${TARGET}/release"
 
 echo "=== Creating k-os boot disk image ==="
 
-# Create and format FAT16 image (mtools required: brew install mtools)
 dd if=/dev/zero of="${IMG}" bs=1K count=${IMG_SIZE_KB} 2>/dev/null
 mformat -i "${IMG}" -t 8 -h 2 -s 32 -r 16 -c 1 -M 512 ::
 echo "Created and formatted ${IMG} (${IMG_SIZE_KB}KB, FAT16)"
 
-# Create directories
-mmd -i "${IMG}" ::servers 2>/dev/null || true
-mmd -i "${IMG}" ::apps 2>/dev/null || true
-
-# Copy init
-if [ -f "${BUILD_DIR}/init" ]; then
-    mcopy -i "${IMG}" "${BUILD_DIR}/init" "::init.elf"
-    echo "  Copied init.elf ($(stat -f%z "${BUILD_DIR}/init" 2>/dev/null || stat -c%s "${BUILD_DIR}/init") bytes)"
-fi
-
-# Copy server binaries
-for server in display-server input-server log-server permission-manager storage-server session-server; do
-    if [ -f "${BUILD_DIR}/${server}" ]; then
-        mcopy -i "${IMG}" "${BUILD_DIR}/${server}" "::servers/${server}.elf"
-        echo "  Copied servers/${server}.elf"
+# Copy with 8.3 names (no long filenames, no tilde mangling)
+copy() {
+    local src="$1" dst="$2"
+    if [ -f "${BUILD_DIR}/${src}" ]; then
+        mcopy -i "${IMG}" "${BUILD_DIR}/${src}" "::${dst}"
+        echo "  ${dst}"
     fi
-done
+}
 
-# Copy app binaries
-for app in snake; do
-    if [ -f "${BUILD_DIR}/${app}" ]; then
-        mcopy -i "${IMG}" "${BUILD_DIR}/${app}" "::apps/${app}.elf"
-        echo "  Copied apps/${app}.elf"
-    fi
-done
+copy init       "init.elf"
+copy echo       "echo.elf"
+copy snake      "snake.elf"
+copy display-server "display.elf"
+copy input-server   "input.elf"
+copy log-server     "log.elf"
+copy permission-manager "permis.elf"
+copy storage-server "storage.elf"
+copy session-server "session.elf"
 
-# List contents
 echo ""
 echo "Disk contents:"
 mdir -i "${IMG}" ::
-mdir -i "${IMG}" ::servers 2>/dev/null || true
-mdir -i "${IMG}" ::apps 2>/dev/null || true
-
-echo ""
 echo "=== Done: ${IMG} ==="