style(simulation): gate bounce — box GenCompletion::BodyAnalyzed state; clippy/fmt sweeps

BodyWorldState grew past clippy's large-enum-variant threshold when it
began retaining Layer1Output (T-1170 Ruling 4b) — boxed, with the two
insert sites deref'd; manual_contains x2 (drainage tests),
cloned_ref_to_slice_refs x3 (river_course tests), fmt wraps.
gen_queue 18/18; clippy -D warnings clean; fmt --check clean.

Tickets: T-1170

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

server/src/atlas/drainage.rs

@@ -1129,8 +1129,7 @@ mod tests {
         let rn = &result.river_network;
         assert!(!rn.mouths.is_empty(), "GJ1c should have real sea mouths");
 
-        let mouth_set: std::collections::BTreeSet<(u16, u16)> =
-            rn.mouths.iter().copied().collect();
+        let mouth_set: std::collections::BTreeSet<(u16, u16)> = rn.mouths.iter().copied().collect();
         for (i, &pos) in rn.river_cells.iter().enumerate() {
             let is_mouth_sentinel = rn.river_downstream[i] == RIVER_DOWNSTREAM_MOUTH;
             let is_in_mouths_list = mouth_set.contains(&pos);
@@ -1195,9 +1194,7 @@ mod tests {
              empty river_cells silently no-ops every assertion below"
         );
         assert!(
-            rn.river_downstream
-                .iter()
-                .any(|&v| v == RIVER_DOWNSTREAM_EDGE_DRAIN),
+            rn.river_downstream.contains(&RIVER_DOWNSTREAM_EDGE_DRAIN),
             "expected at least one EDGE_DRAIN-sentinel river cell (the flat-plateau case) \
              on this fixture — downstream values were {:?}",
             rn.river_downstream
@@ -1208,9 +1205,7 @@ mod tests {
             rn.mouths
         );
         assert!(
-            !rn.river_downstream
-                .iter()
-                .any(|&v| v == RIVER_DOWNSTREAM_MOUTH),
+            !rn.river_downstream.contains(&RIVER_DOWNSTREAM_MOUTH),
             "an all-land world must never emit a MOUTH sentinel"
         );
     }