feat(fls): Java's view of the e-mail programs

The Java view now reads what FILIUS 2.14 keeps for its e-mail programs:
the server's domain, switch and bean accounts with their mailboxes, and the
accounts of /mailserver/konten.txt, which Java reads at every simulation
start and which so win over the bean list; the client's three folders and
address book, and its account from /konten.txt (no bean holds it).

javaEmail.ts ports the bean setters and both file readers
(stringZuListeBenutzerkonten, EmailKonto(String)); javaString.ts Java's
trim, split and StringTokenizer; javaFileSystem.ts the file lookup, now
shared with the DNS server, with the four non-ASCII units Java's
equalsIgnoreCase also takes for an ASCII letter (measured over the BMP).

Checked against Java on the corpus (the oracle dumps the e-mail state) and
on 43 account files read by EmailServer.kontenLaden and
EmailAnwendung.laden (EmailFileCases). Found: older files keep recipients
as strings in the typed lists; a getter copy of the sender is filled and
set back; one short server line makes Java throw for the whole file; a
message with an empty text is lost on reading; a broken last client line
empties the account.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/fls/src/javaString.ts

@@ -0,0 +1,24 @@
+// java.lang.String and java.util.StringTokenizer as FILIUS's text formats
+// use them — each differs from its JavaScript namesake.
+
+/** `String.trim()`: every UTF-16 unit up to U+0020 off both ends. */
+export function javaTrim(text: string): string {
+  return text.replace(/^[\u0000-\u0020]+|[\u0000-\u0020]+$/g, '');
+}
+
+/**
+ * `text.split(separator)` for a one-character separator: trailing empty
+ * parts are dropped — "a;b;;".split(";") is two parts, ";;" none — but a
+ * text without the separator is one part, even the empty text.
+ */
+export function javaSplit(text: string, separator: string): string[] {
+  if (!text.includes(separator)) return [text];
+  const parts = text.split(separator);
+  while (parts.length > 0 && parts[parts.length - 1] === '') parts.pop();
+  return parts;
+}
+
+/** `new StringTokenizer(text, separator)`: the non-empty runs between separators. */
+export function javaTokens(text: string, separator: string): string[] {
+  return text.split(separator).filter((token) => token !== '');
+}