[BUG] CTRL+Z will brick your claude code instance

## Bug Description

Pressing CTRL+Z while in terminal mode on a running claude code window places it into a background state:

```
Claude Code has been suspended. Run `fg` to bring Claude Code back.
Note: ctrl + z now suspends Claude Code, ctrl + _ undoes input.
```

After this, no amount of stopping, closing, restarting seems to get it back. You basically have to exit vim and start it again as far as I can tell.

## To Reproduce

See above

## Expected Behavior

Suspend vim entirely as if you were in any other window, rather than suspending the nested instance.

## Environment

- Neovim version: 0.11.5
- Claude Code CLI version: 2.1.45
- OS: rocky linux
- Plugin version: aa9a5

## Error Messages

N/A

## Additional Context

This works for me as a workaround:
```
vim.api.nvim_create_autocmd("TermOpen", {
callback = function(ev)
local buf_name = vim.api.nvim_buf_get_name(ev.buf)
if buf_name:match("claude") then
vim.keymap.set("t", "", "suspend", {
buffer = ev.buf,
desc = "Suspend Vim from Claude terminal",
})
end
end,
})
```

まず、記載されている Neovim と Claude Code のバージョンでターミナルモードの CTRL+Z を再現し、次に workaround に示されている TermOpen callback と terminal-mode mapping を調べます。CTRL+Z によって外側の Neovim インスタンスが期待どおり suspend され、Claude Code terminal が使用不能にならなければ完了です。

索引モデルが issue の本文から書いたものです。