feat(smart-filter): add auto_enter and confirm_keys options

[robertoash]

Summary

• Adds auto_enter option (default true) to disable automatic directory entry when only one match remains. Useful when you type fast and the plugin enters a directory mid-streak.
• Adds confirm_keys option (default {}) to define extra characters that confirm the current match — entering a directory or opening a file — in addition to <Enter>. For example, { " " } makes Space act as a confirm key.

Both options default to the original behavior, so this is fully backward-compatible.

Example

-- ~/.config/yazi/init.lua
require("smart-filter"):setup {
  auto_enter   = false,   -- don't enter dirs mid-typing
  confirm_keys = { " " }, -- Space also confirms
}