fix(server): a member's test run can no longer freeze the box

On 11-02 open sessions plus test runs filled RAM and the 4 GB swap on a
slow disk; the box hung until a hard reset. Member panes now start at
nice 10, IO priority 7 and oom_score_adj 500 with Vitest capped at 2
workers by default, and the system unit caps its cgroup (server + every
pane) at 85% of RAM with 1G swap and OOMPolicy=continue, so the kernel
kills the biggest pane process instead of hanging the machine. Needs
`agenthub server install-system` once.

scripts/server/install-system.sh

@@ -20,7 +20,8 @@
 #   /etc/sudoers.d/agenthub       checked with visudo before it is installed
 #   /etc/claude-code/managed-settings.json  the member hooks (never over a foreign file)
 #   /proc hidepid=invisible,gid=agenthub-proc  (now and in /etc/fstab)
-#   /etc/systemd/system/agenthub.service    reads the host-owned env file
+#   /etc/systemd/system/agenthub.service    reads the host-owned env file; caps
+#            the cgroup (server + every pane) at 85% of RAM, 1G swap
 # @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 set -euo pipefail
 
@@ -203,6 +204,14 @@ ExecStart=/usr/bin/env \${AGENTHUB_NODE} \${AGENTHUB_ROOT}/server/index.js
 Restart=always
 RestartSec=3
 KillMode=process
+# Every member pane lives in this cgroup. Capped below RAM with little swap
+# (swap on a slow disk froze the whole box on 11-02), a runaway test run is
+# OOM-killed inside the unit — pane-launch makes panes the first pick — and
+# "continue" keeps the dashboard up when that happens.
+MemoryMax=85%
+MemorySwapMax=1G
+OOMPolicy=continue
+OOMScoreAdjust=-100
 
 [Install]
 WantedBy=multi-user.target

scripts/server/pane-launch.sh

@@ -10,7 +10,8 @@
 # the environment and execs the command; no shell ever parses a value.
 #
 # The file is NUL-separated: the number of environment entries, the
-# NAME=value entries, then the argv (none = a login shell).
+# NAME=value entries, then the argv (none = a login shell). Every pane starts
+# at a lower CPU/IO priority and as the kernel's first OOM pick (see below).
 # @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 set -eu
 f=${1:?usage: pane-launch <launch file>}
@@ -22,6 +23,20 @@ for kv in "${parts[@]:1:n}"; do
   [[ "$kv" =~ ^[A-Za-z_][A-Za-z0-9_]*= ]] || { echo "pane-launch: bad variable" >&2; exit 2; }
   export "$kv"
 done
+# A member's pane shares the 4-core box with the dashboard and every other
+# member: its test run, build or dev server must slow down before anything
+# else does, and die first if memory runs out (11-02: 36 sessions plus test
+# runs filled RAM and swap, and the box froze until a hard reset). A member
+# cannot take the nice back (that needs root); oom_score_adj they can lower
+# only to the unit's own -100, and even then the biggest process dies. The unit
+# caps the whole cgroup below RAM (install-system.sh), so the kernel's pick
+# inside it is the biggest pane process, never the dashboard or tmux.
+renice -n 10 -p $$ >/dev/null 2>&1 || true
+ionice -c 2 -n 7 -p $$ >/dev/null 2>&1 || true
+echo 500 >/proc/self/oom_score_adj 2>/dev/null || true
+# Vitest ≤ 3 starts one worker per core by default and these override the
+# config; a member may set their own in the pane.
+export VITEST_MAX_THREADS="${VITEST_MAX_THREADS:-2}" VITEST_MAX_FORKS="${VITEST_MAX_FORKS:-2}"
 argv=("${parts[@]:n+1}")
 if [ ${#argv[@]} -eq 0 ]; then exec -l "${SHELL:-/bin/bash}"; fi
 exec "${argv[@]}"