feat(fls): export the editor model's files

exportProject.ts, step X3: the files of a PC or notebook from the model's
virtual file system under Java's root. A file's type follows from its kind:
text by a known extension (else "text"), an image or binary data by its
media type. Images and binary data are Base64 as FILIUS's
Base64.encodeBytes (iHarder 2.x) writes it: a line break after every 76
characters, also after the last full line. Without that, all 31 images of
the corpus came back with other content. A new oracle tool, Base64Cases,
has Java encode 19 lengths around the line length; javaBase64 matches all.
A router or home router keeps the files its constructor makes.

Checked by Java: every corpus file, imported, exported and written, loads
with the files of the original, byte for byte, up to named departures of
the model: files in its order (directories first, then by name), with the
type of their kind rather than the one the file named (Java itself names
them unevenly), and no router files beyond the constructor's (www.conf,
16 times). The synthetic model adds nested directories, text with and
without a known extension, a PNG, a JPEG, binary data with and without a
media type and 57 bytes, one Base64 line exactly. 10 mutation probes, each
loaded by Java, were all caught.

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

tools/java-oracle/src/Base64Cases.java

@@ -0,0 +1,32 @@
+// Runs FILIUS's own Base64.encodeBytes on byte arrays of the given lengths
+// and writes what Java returns — the reference for javaBase64 in
+// packages/fls/src/exportProject.ts. The bytes of length n are
+// (index * 37 + 11) mod 256, so both sides make them alike.
+//
+// Usage: java -cp filius.jar:lib/*:classes Base64Cases <output json> <length>...
+
+import filius.rahmenprogramm.Base64;
+
+import java.io.FileOutputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class Base64Cases {
+
+    public static void main(String[] args) throws Exception {
+        List<Object> result = new ArrayList<>();
+        for (int argument = 1; argument < args.length; argument++) {
+            int length = Integer.parseInt(args[argument]);
+            byte[] bytes = new byte[length];
+            for (int index = 0; index < length; index++) bytes[index] = (byte) ((index * 37 + 11) % 256);
+            result.add(Arrays.asList(length, Base64.encodeBytes(bytes)));
+        }
+        try (FileOutputStream out = new FileOutputStream(args[0])) {
+            out.write((FlsOracle.Json.write(result, "") + "\n").getBytes(StandardCharsets.UTF_8));
+        }
+        System.out.println("base64 cases: " + result.size());
+        System.exit(0);
+    }
+}