fix(ci): unassign-stale skips long-running label that doesn't exist

[btwshivam]

the stale-claim sweep tries to skip issues marked long-running:

// .github/workflows/unassign-stale.yml:54
if (labels.includes('pinned') || labels.includes('long-running')) continue;

gh label list -R optiqor/optiqor-cli doesn't include long-running. the skip is dead code. pinned exists so the parallel branch works, which is what makes the dead branch easy to miss.

either:

1. create the long-running label and document when a maintainer should apply it
2. drop the long-running clause and update the comment that promises the exception

pick whichever matches actual intent. one-liner either way.