fix(cli): pass --model through to the TUI entry

The root command accepted --model but dropped it before the TUI started, so `opencode --model <id> --prompt ...` silently ran on the configured default model. Pass the flag through to the TUI args, where the existing args.model handling parses it and selects the model — matching the run path's behavior.

Author: holny

packages/cli/src/commands/commands.ts

@@ -55,6 +55,11 @@ const Root = Spec.make(typeof OPENCODE_CLI_NAME === "string" ? OPENCODE_CLI_NAME
       Flag.optional,
     ),
     prompt: Flag.string("prompt").pipe(Flag.withDescription("Prompt to use"), Flag.optional),
+    model: Flag.string("model").pipe(
+      Flag.withAlias("m"),
+      Flag.withDescription("Model to use in the format provider/model#variant"),
+      Flag.optional,
+    ),
   },
   commands: [
     Spec.make("upgrade", {

packages/cli/src/commands/handlers/default.ts

@@ -76,6 +76,7 @@ export default Runtime.handler(Commands, (input) =>
         continue: input.continue,
         sessionID: Option.getOrUndefined(input.session),
         prompt: Option.getOrUndefined(input.prompt),
+        model: Option.getOrUndefined(input.model),
         auto: input.auto || input.yolo || input.dangerouslySkipPermissions,
       },
       config: {