A removed session can no longer be the delivery owner of its continuable
children, but the `host/session-removed` handler only reconciled the
removed row's own activity. `parentAvailable` was updated exclusively from
`refreshSubagents` success, and removal schedules no catalog refresh — so
after the parent's Activation detaches, an addressed child kept a writable
editor against a dead continuation owner until an unrelated refresh (or
forever, for a closed menu).
Flip `parentAvailable` to false on the owned catalog and push
`handleSubagentParentAvailable(false)` to every addressed child Session at
removal time, matching the refresh path's notification. New Session
instances already read `parentAvailable` from the catalog, so they inherit
the invalidated state.
Adds a regression test: removing the catalog's owning parent flips the
snapshot's `parentAvailable` and notifies the addressed child instance.
`refreshSubagents` single-flights per catalog owner: a request arriving
while a pull is in flight returns the in-flight promise and is silently
coalesced into it. The in-flight response was requested before the
triggering change, so it can never contain that change — a debounced
membership refresh (50ms after `host/session-added`) firing during a slow
pull therefore lost the new child, and the catalog stayed stale until an
unrelated trigger (reselection, menu reopen, reconnect).
Mark the owner stale on coalescing and re-arm one trailing pull in the
settlement `finally`, so every membership change observed during a pull is
carried by a follow-up refresh exactly once. Bounded: the trailing pull
only runs when a refresh request was actually coalesced, and a new
coalescing during the trailing pull re-marks the same set.
Adds a fake-timer regression test: a `host/session-added` debounce firing
mid-pull yields exactly two `subagent.list` calls and the catalog
eventually contains the new child.
The fork button on a stopped assistant message was inert. Frozen
interrupted nodes carry a flow-ordering seq of turnEnd.seq - 0.9, and
session.fork takes a non-negative integer on the wire, so every such
request was rejected as invalid-params before reaching the host — where
an aborted turn's logged turn/end has always made it forkable.
SessionsService.fork floors atSeq at the wire boundary. Flooring stays
inside the anchor's own turn (every turn opens with turn/start), so the
host's first-turn/end-at-or-after cut still closes on that turn.
