fix(memory): use edge role=child (valid EA2 vocab)

Probed backend's defines edge role vocabulary. Accepted: child,
dispatch. Rejected: memory, observation, note, recall, vault, step,
view. Switching from invalid 'memory' to valid 'child' so the edge
attach actually lands without 500.

src/lib/agentMemory.ts

@@ -94,7 +94,7 @@ export const agentMemory = {
         body: JSON.stringify({
           request_id: newRequestId(),
           ops: [
-            { op: "create_edge", edge_coll: "defines", from: `flow/${vaultKey}`, to: `flow/${mem._key}`, role: "memory" },
+            { op: "create_edge", edge_coll: "defines", from: `flow/${vaultKey}`, to: `flow/${mem._key}`, role: "child" },
           ],
         }),
         signal,
@@ -116,7 +116,7 @@ export const agentMemory = {
     if (!edgesRes.ok) return [];
     const edges = (await edgesRes.json())?.items || [];
     const memKeys = (edges as any[])
-      .filter((e) => e?.role === "memory" || e?.role === "presentation")
+      .filter((e) => e?.role === "child" || e?.role === "presentation")
       .map((e) => (e._to || "").split("/").pop())
       .filter(Boolean)
       .slice(0, cap) as string[];