Backport #37631 by @silverwind
`UpdateLog` short-circuits on `len(Rows)==0` before honoring `NoMore`,
so a final empty `UpdateLog{NoMore:true}` never runs `TransferLogs`. The
task's `dbfs_data` rows are then never moved to log storage and never
deleted.
The bug has been latent since the original Actions implementation,
`act_runner` versions after
[runner#819](https://gitea.com/gitea/runner/pulls/819) trip it
deterministically.
Fix: let `NoMore=true` with no new rows fall through to `TransferLogs`.
Bail when the runner has outrun the server (`Index > ack`) even with
`NoMore`, since archiving a log with a gap is worse than retrying.
Always call `WriteLogs` so `offset==0` bootstraps an empty DBFS file in
the no-output case (otherwise `TransferLogs` would fail at `dbfs.Open`).
Fixes: https://github.com/go-gitea/gitea/issues/37623
Ref: [runner#952](https://gitea.com/gitea/runner/pulls/952)
Ref: [runner#950](https://gitea.com/gitea/runner/pulls/950)
---
This PR was written with the help of Claude Opus 4.7
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>
