Support non-alphanumeric characters in snippet prefixes

[bitfield]

Check for existing issues

• Completed

Describe the feature

I'd like to be able to define snippets whose prefixes include non-alphanumeric characters. This is supported by VS Code, and I use it to define a "smart quotes" snippet, for example:

 {
  "smart quotes": {
    "prefix": "\"\"",
    "body": ["“$1”"]
  },
}

Thus, typing two " characters in the buffer inserts a pair of matched curly quotes, and leaves the cursor inside them to enter some quoted text.

A little experimentation with Zed suggests that, while prefixes can contain non-alphanumeric characters, as soon as you type that character in the editor, the suggested completion disappears. For example, if you define this snippet:

{
  "test snippet": {
    "prefix": "a@",
    "body": "this is the snippet"
  },
}

and you type a in the editor, the suggested a@ completion is displayed, and you can complete it with Tab/Enter, but if you instead type @, the completion disappears and is no longer available. That means you can't complete a snippet whose prefix begins with a non-alphanumeric character, for example.

If applicable, add mockups / screenshots to help present your vision of the feature

No response