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/domain/src/memory/mod.rs

@@ -104,10 +104,11 @@ impl RegionTable {
         base: PhysicalAddress,
     ) -> Option<(RegionId, &MemoryRegion)> {
         for (i, slot) in self.regions.iter().enumerate() {
-            if let Some(region) = slot {
-                if region.owner() == owner && region.base() == base {
-                    return Some((RegionId::from_raw(i as u16), region));
-                }
+            if let Some(region) = slot
+                && region.owner() == owner
+                && region.base() == base
+            {
+                return Some((RegionId::from_raw(i as u16), region));
             }
         }
         None
@@ -120,3 +121,9 @@ impl RegionTable {
             .filter(move |r| r.owner() == process)
     }
 }
+
+impl Default for RegionTable {
+    fn default() -> Self {
+        Self::new()
+    }
+}