feat(opencode): add oh-my-openagent plugin with omo config for ollama-cloud/glm-5.1

Configure oh-my-openagent (omo) plugin for multi-agent orchestration
using ollama-cloud and local llama-swap providers. Primary model is
ollama-cloud/glm-5.1 with fallback chains. Add runtime fallback,
background task concurrency limits, and disable incompatible agents
(hephaestus, multimodal-looker).

home/roles/base/default.nix

@@ -103,6 +103,10 @@ in
       source = ./opencode-config.json;
     };
 
+    xdg.configFile."opencode/oh-my-openagent.jsonc" = {
+      source = ./opencode-omo-config.jsonc;
+    };
+
     # Note: modules must be imported at top-level home config
   };
 }