Make the Rust suite green and stop silently ignoring packages

exact_reliable_acks_clear_more_than_one_ack_window_of_fragments has been
failing on main. It was not a defect: send_many returned 32 packets where the
test expected 40, and 32 is exactly CULTNET_RUDP_RELIABLE_SEND_WINDOW_PACKETS.
The reliable send window landed and this test kept asserting the pre-window
behaviour, so a test whose name is about crossing an ack window had stopped
crossing one. It now asserts that a window's worth leaves immediately, that
the remaining eight fragments queue, and that acknowledgements promote them
until every fragment is delivered -- the same loop packages/cultnet-rs/tests
/cultnet.rs already uses for this contract.

All three Rust crates are green: 46, 95 and 7.

The NuGet packages rule hides every language package until one is named in
the re-include list, and cultmath, cultmesh-browser and cultmesh-kotlin were
never added. Nothing is currently lost -- every source file in them is
tracked -- but any new file added to those three would have been dropped in
silence. cultmesh-rs hit this on the way in.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.gitignore

@@ -309,6 +309,12 @@ node_modules/
 !packages/cultnet-rs/**
 !packages/cultmesh-rs/
 !packages/cultmesh-rs/**
+!packages/cultmath/
+!packages/cultmath/**
+!packages/cultmesh-browser/
+!packages/cultmesh-browser/**
+!packages/cultmesh-kotlin/
+!packages/cultmesh-kotlin/**
 packages/**/node_modules/
 packages/**/dist/
 packages/**/dist-test/