fix: sched round-robin, cap slot OOB panic, clippy, make ci

- RunList -> intrusive FIFO, no starvation, no silent drop
- cap table sized to CapSlot range (kani caught OOB panic)
- snake food color test uses const
- kani cfg lint, RUST_MIN_STACK for big kernel struct in tests

crates/kernel/src/syscall/capability.rs

@@ -42,11 +42,11 @@ impl<P: Platform> Kernel<P> {
             return SyscallOutcome::Complete(SyscallResult::Error(e));
         }
 
-        if let domain::resource::Resource::Memory(region_id) = &resource {
-            if let Some(region) = self.regions.get(*region_id) {
-                self.platform
-                    .map_shared(target_pid, region.base(), region.size(), restricted);
-            }
+        if let domain::resource::Resource::Memory(region_id) = &resource
+            && let Some(region) = self.regions.get(*region_id)
+        {
+            self.platform
+                .map_shared(target_pid, region.base(), region.size(), restricted);
         }
 
         SyscallOutcome::Complete(SyscallResult::Ok)