ci: clarify Postgres service hostname for Gitea act_runner vs VM runners

Merge duplicate comments from CI workflow conflict resolution.

Co-authored-by: Cursor <cursoragent@cursor.com>

.github/workflows/ci.yml

@@ -60,7 +60,8 @@ jobs:
           --health-retries 5
         ports:
           - 5432:5432
-    # Hostname must match `services:` id. `localhost` breaks Gitea act_runner (Docker job).
+    # Hostname must match `services:` id. `localhost` breaks Gitea act_runner (Docker job);
+    # use the service name for Dockerized runners; VM runners may map host ports differently.
     env:
       DATABASE_URL: postgresql://postgres:postgres@postgres:5432/test
       TEST_DATABASE_URL: postgresql://postgres:postgres@postgres:5432/test