fix(command-loader): preserve model field for opencode commands only

- Claude Code commands (user, project scope): sanitize model to undefined
- OpenCode commands (opencode, opencode-project scope): preserve model as-is

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/features/claude-code-command-loader/loader.ts

@@ -34,12 +34,13 @@ $ARGUMENTS
 
       const formattedDescription = `(${scope}) ${data.description || ""}`
 
+      const isOpencodeSource = scope === "opencode" || scope === "opencode-project"
       const definition: CommandDefinition = {
         name: commandName,
         description: formattedDescription,
         template: wrappedTemplate,
         agent: data.agent,
-        model: sanitizeModelField(data.model),
+        model: sanitizeModelField(data.model, isOpencodeSource ? "opencode" : "claude-code"),
         subtask: data.subtask,
         argumentHint: data["argument-hint"],
       }