KYAML encoder (kubectl -o kyaml) corrupts lines starting with \r, NBSP, U+3000

sigs.k8s.io/yaml/kyaml v1.6.0 (&kyaml.Encoder{}).Marshal("para1\r\n\r\npara2") writes a folded double-quoted string whose third line is \\r\n\. Parsers read that as an escaped backslash followed by 'r', so a literal backslash appears in the value. It hits any line of a multi-line string that starts with \r (CRLF text with blank lines), \v, \f, NBSP, U+2000-U+200A, U+2028/9 or U+3000 (the Japanese paragraph indent). Cause: appendEscapedRune adds a '\\' before leading whitespace when unicode.IsSpace(r) is true, so that folding doesn't strip it, but only ' ' and '\t' are written raw; everything else already becomes its own escape sequence. Fix: prefix only ' ' and '\t'. The 1000-iteration randfill round-trip test never generates '\n' followed by these runes, which is why it passes. Compact: true output is unaffected. A targeted round trip of strings with odd whitespace after a newline found this in one run.