feat(FN-3620): wire Hermes chat message tools and document mailbox behavior

Merges FN-3620, completing the Hermes chat mailbox integration with wired message tools, locked sender/recipient contract tests, and mailbox behavior documentation, plus a small CSS polish adding `focus-visible` styles and token radius to the render toggle. A changeset for FN-3710 (cluster task ID o

Fusion-Task-Id: FN-3620

packages/dashboard/src/server.ts

@@ -942,6 +942,7 @@ export function createServer(store: TaskStore, options?: ServerOptions): ReturnT
     chatAgentStore,
     options?.pluginRunner,
     () => store.getSettings(),
+    options?.engine?.getMessageStore(),
   );
 
   const runAiSessionCleanup = (maxAgeMs: number, source: "initial" | "scheduled") => {