ADR 0589 version 29, clause 6. At start and after a catch-up an address key is an expiry never heard only when its
enrolment key is gone and the router records its ask answered yes; one declined or not answered yet is no expiry, and one
not answered stays until its ask ends. A confirm, a decline and a refused add delete the address key before their other
steps, so one stopped midway never leaves a key the catch-up would take for an expiry and unplace a node that joined. A
refused add (mesh-placement's refusal of the proposal, not a call that did not reach it) now ends the enrolment as refused;
a call that failed still waits for again. Tests: rows in the end table (after a confirm stopped before its enrolment key
went, after a decline, after a refused add, a declined ask, an ask not answered: nothing unplaced) and the integration test's
holder-was-down case reading the yes; no new function.
(issue 774)
Claude-Session: https://claude.ai/code/session_01NcbgfJ9Gum47zkFKWRaovL
jschoubben
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