Feature Request: Support for Snippet Variables (e.g., TM_FILENAME, TM_FILENAME_BASE)

[erikbachman]

Currently, the snippet parser in Zed does not support variables. It would be very useful if we could use variables in snippets, such as TM_FILENAME, TM_FILENAME_BASE, CURRENT_YEAR, etc., just like in VSCode.

Expected Behavior:
The snippet parser should recognize and replace variables such as:

• $TM_FILENAME - current file name
• $TM_FILENAME_BASE - current file name without extension
• $TM_CURRENT_LINE - current line content
• $TM_SELECTED_TEXT - currently selected text
• $CURRENT_YEAR, $CURRENT_MONTH, $CURRENT_DATE - time-related variables
• $CLIPBOARD - clipboard content

Use Case Examples:

// File header snippet
/**
 * $TM_FILENAME
 * Created on $CURRENT_YEAR-$CURRENT_MONTH-$CURRENT_DATE
 */

// React component snippet
const ${1:Component} = () => {
  return (
    <div>$TM_SELECTED_TEXT</div>
  );
};

export default $1;

Benefits:
This would make snippets much more powerful and context-aware, significantly improving developer productivity when working with file-specific or time-sensitive templates.

---