dmesg came back empty, and the evidence that actually settles it was in the original log the whole time. Step 7 `Run migrations` succeeded, then step 9's globalSetup applied all six migrations again from scratch. Both point at the same database — migrate.js reads PGHOST/PGDATABASE and the job sets those and TEST_PG* to the same service and the same redefined_test — so had step 7 migrated it, globalSetup would have printed "No migrations to run!", which is what a local run prints.
It found an empty database. The wipe was already happening before the tests started, which makes this a database being reset repeatedly rather than a container dying partway through a heavy run, and accounts cleanly for the empty dmesg: a restart is not a kill.
The suspect moves from memory pressure to the runner's handling of `services:`, where act_runner has been uneven across releases. The diagnostics change with it: A3 is dropped because it was designed to catch starvation, A2 is demoted to a fallback, and the new first check needs nothing but the Gitea UI — compare step 7 and step 9's migration output in any failing run.
The superseded hypothesis is kept rather than deleted. A future reader finding memory ruled out is better served by seeing why it was suspected and what refuted it than by a document that never mentions it.
Refs #154
bermudalamb