repo_description: Why is this running?
code: package output
  
  import (
  	"strings"
  	"unicode"
  	"unicode/utf8"
  )
  
  const hexDigits = "0123456789abcdef"
  
  // SanitizeTerminal makes a string safe to print to an interactive terminal
  // by just replacing control characters with visible escape sequences (e.g. "\x1b")
  // Examples:
  //   - "hi\x1b[31mred" -> "hi\x1b[31mred" (ESC becomes visible)
  //   - "nul:\x00"      -> "nul:\x00"
  //   - "bad:\xff"      -> "bad:\xff" (invalid UTF-8 byte)
  //   - "a\tb\nc"        -> "a\tb\nc" (tabs/newlines are untouched)
  func SanitizeTerminal(s string) string {
  	idx := 0
  	// fast path: scan until we find a control rune / invalid UTF-8 byte
  	for idx < len(s) {
  		r, size := utf8.DecodeRuneInString(s[idx:])
  		if r == utf8.RuneError && size == 1 {
  			break
  		}
  		if r == '\n' || r == '\t' {
  			idx += size
  			continue
  		}
  		if unicode.IsControl(r) {
  			break
  		}
  		idx += size
  	}
  	if idx == len(s) {
  		return s
  	}
  
  	var b strings.Builder
  	b.Grow(len(s) + 8)
  	b.WriteString(s[:idx])
  
  	// slow path: walk the remainder and rewrite any control bytes/runes
  	for idx < len(s) {
  		r, size := utf8.DecodeRuneInString(s[idx:])
  		if r == utf8.RuneError && size == 1 {
  			// preserve invalid bytes without letting them act as controls just in case
  			appendEscapedByte(&b, s[idx])
  			idx++
  			continue
  		}
  
  		if r == '\n' || r == '\t' {
  			b.WriteRune(r)
  			idx += size
  			continue
  		}
  
  		if unicode.IsControl(r) {
  			appendEscapedRune(&b, r)
  			idx += size
  			continue
  		}
  		b.WriteString(s[idx : idx+size])
  		idx += size
  	}
  
  	return b.String()
  }
  
  func appendEscapedByte(b *strings.Builder, bt byte) {
  	b.WriteString(`\\x`)
  	b.WriteByte(hexDigits[bt>>4])
  	b.WriteByte(hexDigits[bt&0x0f])
  }
  
  // while this looks extremely bad, it just outputs this:
  //   - r = 0x1b     -> "\x1b"
  //   - r = 0x2028   -> "\u2028"
  //   - r = 0x1f600  -> "\U0001f600"
  func appendEscapedRune(b *strings.Builder, r rune) {
  	// 0xFF: "\xHH" (simple byte escape)
  	if r <= 0xFF {
  		appendEscapedByte(b, byte(r))
  		return
  	}
  
  	// <= 0xFFFF: "\uHHHH" (BMP escape)
  	if r <= 0xFFFF {
  		b.WriteString(`\\u`)
  		b.WriteByte(hexDigits[(r>>12)&0x0f])
  		b.WriteByte(hexDigits[(r>>8)&0x0f])
  		b.WriteByte(hexDigits[(r>>4)&0x0f])
  		b.WriteByte(hexDigits[r&0x0f])
  		return
  	}
  
  	// otherwise: "\UHHHHHHHH" (full 32-bit escape)
  	b.WriteString(`\\U`)
  	b.WriteByte(hexDigits[(r>>28)&0x0f])
  	b.WriteByte(hexDigits[(r>>24)&0x0f])
  	b.WriteByte(hexDigits[(r>>20)&0x0f])
  	b.WriteByte(hexDigits[(r>>16)&0x0f])
  	b.WriteByte(hexDigits[(r>>12)&0x0f])
  	b.WriteByte(hexDigits[(r>>8)&0x0f])
  	b.WriteByte(hexDigits[(r>>4)&0x0f])
  	b.WriteByte(hexDigits[r&0x0f])
  }
  