protobuf format mismatch between this and current worldengine?

Start with WorldFileLoaderTest.java and reproduce the failure using seed_17824.world alongside seed_1534.world. Compare how the loader handles the two protobuf formats and identify the compatibility boundary. Done means the current WorldEngine world file loads without the missing-required-fields error and the relevant test passes.

I've tried to use this project to import information from a world file into a Java program (to paint a more detailed river map and a lake map, for example).
But even replacing

public void loadWorld() throws IOException {
    InputStream is = WorldFileLoaderTest.class.getClassLoader().getResourceAsStream("seed_1534.world");
    WorldFile.World worldFile = WorldFileLoader.fromInputStream(is);
    assertEquals("seed_1534", worldFile.getName());
}

with

public void loadWorld() throws IOException {
    InputStream is = WorldFileLoaderTest.class.getClassLoader().getResourceAsStream("seed_17824.world");
    WorldFile.World worldFile = WorldFileLoader.fromInputStream(is);
    //assertEquals("seed_17824", worldFile.getName());
}

in WorldFileLoaderTest.java (after placing the freshly generated seed_17824.world next to seed_1534.world in the filesystem) results in

Tests in error: 
  loadWorld(org.worldengine.world.WorldPainter): Message missing required fields: name, height, heightMapData, heightMapTh_sea, ...

A quick look with ghex into both seed_17824.world and seed_1534.world reveals that they look quite different (obviously only showing the first couple of bytes):

0A 09  s  e  e  d  _  1  5  3  4 10 80 08 18 80 08  " 80 98 C0 04 0A 80
 H 09 00 00 00 00 00 00 00 00 09 00 00 00 00 00 00 00 00 09 00 00 00 00

vs.

08 EE CA BD BB 05 10 80 80  L 1A 0A  s  e  e  d  _  1  7  8  2  4 20 D5
0E  ( F3 06  2 F3 D2 8E 07 0A FD 83 01 09 C2 F5  (  \ 8F C2 D5  ? 09 C2
F5  (  \ 8F C2 D5  ?