tui: fix Windows terminal suspend and input undo keybindings

On Windows, native terminals don't support POSIX suspend (ctrl+z), so we now
assign ctrl+z to input undo instead of terminal suspend. Terminal suspend is
disabled on Windows to avoid conflicts with the undo functionality.

packages/opencode/src/config/config.ts

@@ -19,7 +19,6 @@ import { GlobalBus } from "@/bus/global"
 import { Event } from "../server/event"
 import { Account } from "@/account"
 import { isRecord } from "@/util/record"
-import { InvalidError, JsonError } from "./error"
 import type { ConsoleState } from "./console-state"
 import { AppFileSystem } from "@opencode-ai/shared/filesystem"
 import { InstanceState } from "@/effect"