fix(ark): run as the image's own user; honour custom RCON ports

ARK's image is built around user gameserver (uid 25000) and locks
/home/gameserver to it, so under the node's default 1000:1000 the
startup script got "Permission denied" and the server restart-looped,
on real nodes as well as in boot tests. Set containerUser 25000:25000
(needs node-agent and panel support for containerUser).

The startup command read ${RCON_PORT}, but the node passes the RCONPort
setting as RCONPORT, so custom RCON ports were ignored for 27020.

Boot-tested in the Linux agent image: up 30 minutes with no restart.
The test now waits 10 minutes, covering the first ~13 GB download.

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

games/ark-survival-ascended-crossplay/test.yaml

@@ -1,3 +1,6 @@
 # yaml-language-server: $schema=../../schema/test.schema.json
 # Values CI uses to boot-test this game. Never put real credentials here: map them under 'secrets'.
-timeoutSec: 900
+# No readyPattern yet: the server must stay up for 10 minutes, which covers the ~13 GB first
+# download and Proton's slow first start.
+settleSec: 600
+timeoutSec: 2400