ci: give the runner 5 GB, since the analysis needs 3.7 GB cold

Decided 2026-10-01. CI run #32 died in its analysis: a cold `dart analyze`
of the workspace with the lint plugin now peaks at about 3.7 GB (2.1 GB
warm), measured with an empty analysis cache, while the runner's unit
allowed 3 GB. The kernel killed it, systemd's default OOMPolicy (stop) then
stopped the whole unit, and the job's remaining processes got SIGTERM: the
"signal: terminated" in the log. The packages this branch added tipped it
over.

The runner may now use 5 GB of sahaquiel's 8, and above 4 GB the kernel
reclaims from CI first (MemoryHigh), so the instance keeps at least 3 GB;
it uses under 1 GB today. Installed by hand on sahaquiel, like the rest of
the unit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

deploy/runner/forgejo-runner.service

@@ -66,10 +66,13 @@ SystemCallFilter=~@clock @cpu-emulation @debug @module @mount @obsolete @raw-io
 SystemCallErrorNumber=EPERM
 UMask=0077
 
-# Never at the instance's expense: two of the four cores, 3 GB of the 8, and the lowest
-# priority for CPU and disk.
+# Never at the instance's expense: two of the four cores, at most 5 GB of the 8 (the
+# kernel reclaims from CI first above 4 GB), and the lowest priority for CPU and disk.
+# A cold `dart analyze` of the workspace with its lint plugin needs about 3.7 GB; with
+# 3 GB the kernel killed it, and OOMPolicy's default then stopped the whole unit.
 CPUQuota=200%
-MemoryMax=3G
+MemoryHigh=4G
+MemoryMax=5G
 TasksMax=2048
 Nice=10
 IOSchedulingClass=best-effort