A refcounted id set: acquire/release per mounted consumer, the list of live
ids as state. An id stays live while ANY consumer holds it, so several
surfaces can independently keep the same id registered without racing each
other's teardown — the store-agnostic building block for "a document is
watched while any surface reads it" registration. releaseDelayMs keeps an
id live for a grace period after its last release; reacquiring it cancels the
pending removal.
A refcounted id set: acquire/release per mounted consumer, the list of live ids as state. An id stays live while ANY consumer holds it, so several surfaces can independently keep the same id registered without racing each other's teardown — the store-agnostic building block for "a document is watched while any surface reads it" registration.
releaseDelayMskeeps an id live for a grace period after its last release; reacquiring it cancels the pending removal.