fix(agones): report network player counts, not this proxy's

[hbrombeer]

The bug

Two players standing in the same lobby, each connected through a different proxy. /agones reported (1 players) — on both proxies.

Live from the dev cluster at the time of the report:

 player_name |  proxy_id  |         server_name
 dahendriik  | velocity   | minestom-lobby-2-m4j27-96nxf
 A8K1        | velocity-2 | minestom-lobby-2-m4j27-96nxf

AgonesCommand read server.playersConnected.size and proxyServer.playerCount. Both are proxy-local by definition — Velocity has no idea the other proxy exists. The command printed the half it could see as if it were the whole network.

The fix

Ask ProxyService.getNetworkPlayerCounts(), backed by service-player's session table (which already records proxy_id and server_name for every player).

When the presence service cannot be reached, the counts still render — but the command says they are proxy-local. That matters: an unlabelled local count looks exactly like a network count, which is precisely why this shipped unnoticed. Silently degrading back to the old numbers would be reprinting the bug.

plugin-proxy-api is compileOnly, never shaded: the ProxyServiceRegistry we read must be the same class plugin-proxy loaded, or we would read a registry nobody writes to.

Merge order

Last of 5. Until the ones above land, getNetworkPlayerCounts() returns null and /agones behaves as today, minus the false confidence (it now labels the numbers).

1. feat(player): count online players per backend server library-grpc-contracts#71 → release library-grpc-contracts-player 0.4.0
2. feat(proxy): expose network-wide player counts per backend server plugin-proxy#15 → release plugin-proxy-api 0.2.0
3. service-player — implement the RPC
4. plugin-player — implement countPlayersByServer()
5. this PR

Verified

./gradlew :velocity:test green against locally-published plugin-proxy-api:0.2.0. New tests: two players on one lobby across two proxies read as (2 players); a fallback to proxy-local counts is labelled; a server nobody is on shows (0 players) rather than vanishing.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud