The self-built `ok/err/handle` helpers called `ipcMain.handle` directly,
which meant every OAuth IPC channel skipped the trusted-renderer check
in `ipc-support.registerHandle` and its `ZodError -> IPC_INVALID_PAYLOAD`
sanitizer. Any renderer origin could invoke these channels, and thrown
zod errors would leak the raw validator message.
Take `registerHandle` and `fail` as dependencies so callers wire in the
hardened variants from `createIpcSupport`, drop the local helpers, and
import `ok` from `ipc-core-common`. Zod inputs stay on `safeParse` to
preserve the explicit `INVALID_INPUT` code + message path.
