The stale workflow was hitting its 250 operations-per-run cap every
daily run, causing the "No more operations left! Exiting..." warning
and leaving a growing backlog of stale-labeled items that were never
being closed. GitHub API headroom is plentiful (250 ops uses ~1.6% of
the 15k/hour bucket), so raising to 1500 drains the backlog without
any rate-limit risk.
Also adds workflow_dispatch so maintainers can trigger the workflow
from the Actions tab or via gh workflow run stale.yml.
Signed-off-by: Ramon Roche <mrpollo@gmail.com>
a3ad956394