The identity-guarded token pop appeared twice (the runner's finally and the
new worker-start except); a future edit to one copy would silently reintroduce
the sticky-token class. Hoist into a local closure called from both sites, and
extend the _run_hook_callback_bounded docstring with the new skip reason.
Behavior-preserving follow-up on #104651.
For each issue anchor present in BASE 63279301bc non-test .py and absent on HEAD, the BASE comment/docstring block was re-attached at the HEAD location of the code it explained (matched by the distinctive code line / enclosing def). Sentences already covered by an existing HEAD comment were deduped; the issue number always survives. Insert-only: no code lines changed.
