TRC87: TRACE-KODE-SYSTEM

FEATURES:
1. ONE-WAY ONLY
   - Email cannot be recovered from the trace kode.
   - One-way identity kode.
2. FLOATABLE
   - Trace kodes can be shared freely with zero risk.
   - Called a "mask": visible, shareable, anonymous.
3. DETERMINISTIC
   - Same email always produces same trace kode.
4. KOSMIK KALLISIONS
   - Extremely rare collisions signal something special.

function TRC87($zk) {
    $zk = strtolower(trim($zk));
    $zk = hash('sha256', $zk);
    $zk = substr($zk, 8, 7);
    return $zk;
}

USAGE:
- Input: any email address string.
- Output: 7-character trace kode string.
- Example:
    echo TRC87('zhama@example.wtf'); 
    // outputs something like '1A9F7QZ'

NOTES:
- No salt needed: simplicity, transparency, and one-way guarantee.
- Ideal for small-to-medium groups. Collisions extremely rare and treated as feature.
- Serves as public key/mask in the game for accountability from day 0.