fix(snacks): invalid window on :ClaudeCodeFocus

[qw457812]

Steps to reproduce:

1. :ClaudeCode to open claude code
2. <c-h> to focus main window
3. <c-w>o in main window to close claude code
4. :ClaudeCodeFocus to focus claude code

I got:

Lua :command callback: .../lazy/claudecode.nvim/lua/claudecode/terminal/snacks.lua:213: Invalid window id: 1010
stack traceback:
 [C]: in function 'nvim_set_current_win'
 .../lazy/claudecode.nvim/lua/claudecode/terminal/snacks.lua:213: in function 'focus_toggle'
 ...re/nvim/lazy/claudecode.nvim/lua/claudecode/terminal.lua:257: in function 'focus_toggle'
 .../share/nvim/lazy/claudecode.nvim/lua/claudecode/init.lua:905: in function <.../share/nvim/lazy/claudecode.nvim/lua/claudecode/init.lua:899>

Config:

{
    "coder/claudecode.nvim",
    dependencies = { "folke/snacks.nvim" },
    cmd = "ClaudeCode",
    init = function()
      vim.env.CLAUDE_CONFIG_DIR = vim.fn.expand("~/.config/claude")
    end,
    opts = {},
}