feat(sub-lang): Integrate SUB Language (.sb) native kernel modules and in-kernel VM/interpreter

- Add native .sb kernel modules in sub/ (signature.sb, power_governor.sb, benchmark.sb, easter_egg.sb)
- Implement in-kernel SUB Language VM and AST interpreter in kernel/sub/sub_vm.c
- Implement C-interop runtime in kernel/sub/sub_runtime.c and include/kernel/sub_lang.h
- Initialize SUB Language Engine in boot sequence step [8/14] in kernel/main.c
- Implement strtol in lib/string.c
- Add LazyBox applets: 'subinfo', 'subi', 'subpower', 'subbench', and 'subquote'

rust/src/kernel/watchdog.rs

@@ -12,7 +12,6 @@ pub struct KernelHealthReport {
 pub struct Watchdog {
     heartbeats: u64,
     subsystems_online: u32,
-    last_tick: u64,
 }
 
 impl Watchdog {
@@ -20,7 +19,6 @@ impl Watchdog {
         Self {
             heartbeats: 0,
             subsystems_online: 0,
-            last_tick: 0,
         }
     }