feat(rust): Implement Rust-for-SUB-OS kernel layer, ChaCha20 crypto, HWMON thermal governor, and lazybox applets

- Add freestanding no_std Rust kernel layer compiled with rustc
- Implement memory-safe ChaCha20 RFC-8439 stream cipher and CSPRNG in Rust
- Implement intelligent thermal fan speed governor in Rust
- Add printk macro bridge (kprint!, kprintln!) for Rust
- Register 'rustinfo' and 'chacha20' LazyBox applets
- Enable x86_64 hardware FPU & SSE (CR4.OSFXSR/OSXMMEXCPT)
- Add cross-architecture C-bridge for ARM targets
- Update stage2.asm kernel sector copy bounds to 448 KB

boot/stage2.asm

@@ -93,7 +93,7 @@ start2:
     mov word [kernel_dap_seg], 0x1000
     mov dword [kernel_dap_lba], 16
     mov dword [kernel_dap_lba + 4], 0
-    mov cx, 6                          ; 6 chunks * 64 sectors = 384 sectors (192 KB)
+    mov cx, 14                         ; 14 chunks * 64 sectors = 896 sectors (448 KB)
 
 .kernel_chunk_loop:
     push cx
@@ -199,7 +199,7 @@ pm_entry:
     ; Copy kernel from 0x10000 to 0x100000 (1MB mark) - 192 KB (384 sectors)
     mov esi, 0x10000
     mov edi, 0x100000
-    mov ecx, (384 * 512) / 4
+    mov ecx, (896 * 512) / 4
     rep movsd
 
     ; Enable PAE in CR4