Gating hook callbacks by call identity lets two concurrent calls of the
same tool both run their hooks, but it also let a fresh tool_call_id pass
the gate once the 60 s suppression window lapsed even though the previous
worker for that callback never returned. A hung plugin then leaked one
daemon thread per minute for the life of the process; on the old
coarse-keyed gate it leaked exactly one.
Track abandoned-but-running workers per callback: the timeout branch
records the gate key, the worker's own release discards it, and the gate
treats any non-empty abandoned set as "still running" for that callback.
Healthy callbacks keep distinct-id concurrency; hung ones are back to
at most one outstanding worker.
Move the general-vs-memory hook ownership logic out of the memory collector into
PluginLedgerMixin (_drop_fallback_hooks / _register_fallback_hook) so the collector
and the loader each call one manager method instead of reaching into manager privates.
Hoist hashlib to module scope. Trim the new suite to the three invariant cases
(run-once across load orders, distinct sources not suppressed, re-exported register).
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.
