Fix flaky test Tasks page _ done outcome + false-close warn (_1027 item 12) _ shows the merged-PR link + summary on a confirmed done task, with no warn

The merge lane saw `Tasks page _ done outcome + false-close warn (_1027 item 12) _ shows the merged-PR link + summary on a confirmed done task, with no warn` fail and then pass on a rerun of the same tree. - Test: `Tasks page _ done outcome + false-close warn (_1027 item 12) _ shows the merged-PR link + summary on a confirmed done task, with no warn` - Tree: `29c73882ff4ef86491958ddf890a2480da314249` - Lane task: 11339 - Flake record: 01a188e4-31c1-7163-92e8-fdf4a24408e4 Make it deterministic; do not delete it unless it tests nothing.

The flaky done-outcome case now answers its non-list reads (projects, worktrees, creators, setup) with [] like its siblings. Before, it got a task object, and once the tree emptied with an unhandled error. Quick gate green; 6/6 file runs green; PR #7368 queued. Memory: none applied.