The whole v1.9.0 cycle ran without a version bump, so the plugin still reported
1.8.8 in-game. For a tester beta that is untenable: bug reports would name a
version that does not identify the code they ran.
Download links stay pinned to v1.5.6 on purpose. There is no v1.9.0 release, and
pointing at an artifact that does not exist is worse than the visible mismatch
between assembly version and download target. Public stays on v1.5.6 until
v2.0.0.