fix(ci): increase job container memory limit 512m→768m for harness tests

Sequential jobs (security-gate needs frontend-tests) mean only one container
runs at a time. 768MB + Gitea/Vault/OS ~300MB fits within 1GB+swap headroom.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

AINative_OKR_CASAN5/.gitea/act-runner-config.yaml

@@ -27,10 +27,11 @@ runner:
 container:
   network: bridge
 
-  # --memory 512m: prevent OOM on 1 GB VPS (build runs in HOST daemon, not job container)
+  # --memory 768m: allow harness tests headroom while leaving ~300MB for Gitea/Vault/OS.
+  # Jobs run sequentially (capacity: 1) so two containers never compete.
   # NOTE: act_runner already passes /var/run/docker.sock from its own mounts to job
   # containers; do NOT add it here or Docker will reject the duplicate bind mount.
-  options: "--memory 512m --cpus 1.5"
+  options: "--memory 768m --cpus 1.5"
 
   valid_volumes:
     - "**"