fix(model-fallback): align OpenAI fallback resolution across CLI and runtime

Keep install-time and runtime model tables in sync, stop OpenAI-only misrouting when OpenCode Go is present, and add valid OpenAI fallbacks for atlas, metis, and sisyphus-junior.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/plugin-handlers/agent-config-handler.ts

@@ -158,7 +158,7 @@ export async function applyAgentConfig(params: {
 
     agentConfig["sisyphus-junior"] = createSisyphusJuniorAgentWithOverrides(
       params.pluginConfig.agents?.["sisyphus-junior"],
-      undefined,
+      (builtinAgents.atlas as { model?: string } | undefined)?.model,
       useTaskSystem,
     );