feat(task): runs as a table, last three per target

[jshvn]

Summary

• task runs prints one table in the same style as task targets: JOB, STARTED (UTC), EVENT, RESULT. The job name appears only on its first row.
• It shows the last 3 runs per target by default (was 10); LIMIT= still overrides it.
• An unfinished run shows its status (queued, in_progress) instead of a blank. GitHub returns an empty string for its conclusion, not null, so the old // "running" fallback never fired.

Test plan

• task runs on a terminal and piped: aligned table, header present, in-progress runs labelled
• task runs LIMIT=1