feat(topology): executors for all 12 kinds (mesh + debate; mappings)

Every TopologyKind now runs, mapped to five execution patterns:
- hierarchical ← hub_spoke, star_moe, market
- pipeline     ← ring
- swarm        ← flat, holacratic
- mesh (new)   ← blackboard   (two peer-exchange rounds + aggregate)
- debate (new)                (propose → critique → revise → judge)

execute()'s match is now exhaustive (adding a kind upstream forces an executor),
so the Unsupported error is gone. Benchmark spans all five distinct patterns.
14 tests with --features provider; clippy clean. Doc updated.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

crates/cm-orchestrator/examples/topology_bench.rs

@@ -63,6 +63,28 @@ fn swarm() -> TopologyGraph {
     .unwrap()
 }
 
+fn mesh() -> TopologyGraph {
+    TopologyGraph::new(
+        TopologyKind::Mesh,
+        vec![node("a", "analyst"), node("b", "analyst"), node("c", "analyst")],
+        vec![
+            Edge { from: "a".into(), to: "b".into(), kind: EdgeKind::PeersWith },
+            Edge { from: "b".into(), to: "c".into(), kind: EdgeKind::PeersWith },
+            Edge { from: "a".into(), to: "c".into(), kind: EdgeKind::PeersWith },
+        ],
+    )
+    .unwrap()
+}
+
+fn debate() -> TopologyGraph {
+    TopologyGraph::new(
+        TopologyKind::Debate,
+        vec![node("proposer", "proposer"), node("critic", "critic"), node("judge", "judge")],
+        vec![],
+    )
+    .unwrap()
+}
+
 #[tokio::main]
 async fn main() {
     let (provider, model): (Arc<dyn LlmProvider>, String) =
@@ -78,7 +100,7 @@ async fn main() {
 
     let executor = ProviderExecutor::new(provider, model.clone(), 512);
     let task = "Draft a go-to-market launch plan for a new product.";
-    let graphs = vec![hierarchical(), pipeline(), swarm()];
+    let graphs = vec![hierarchical(), pipeline(), swarm(), mesh(), debate()];
 
     let cmp = compare(&graphs, task, &executor, &LengthScorer)
         .await