Mobile client creates a duplicate session on every reconnect to a remote session; auto-archive on disconnect no longer fires

What happens

Connecting from the mobile client to an existing remote session creates a new
session record with the same title instead of attaching to the existing one.
Previously, disconnecting auto-archived the duplicate, so this was invisible.
That auto-archive no longer happens, so every login/reconnect cycle leaves a
permanent duplicate behind and the session list on the phone grows without bound.

Expected

Reconnecting attaches to the existing session, or — failing that — the duplicate
shell is archived on disconnect as it used to be.

Evidence

From a Claude Code desktop session on the host machine, ListAgents reports 26
peer sessions labeled Remote Control · offline. Grouped by title:

• one title appears 9 times (9 distinct session refs)
• two more titles appear 3 times each
• the remaining 11 titles appear once

So 26 entries correspond to roughly 14 real conversations plus ~12 duplicate
shells. The duplicates carry distinct session refs but identical titles.

These sessions have no record on the host machine: the desktop session store
returns only 5 sessions for this project even with archived included, none of
them matching the duplicated titles, and there are no local transcripts for them
under ~/.claude/projects/. The duplicates therefore exist only account-side and
cannot be cleaned up from the desktop client — only from the phone, by hand.

Environment

• Host: macOS (Darwin 25.6.0), Claude Code desktop app
• Client creating the duplicates: Claude mobile app, Remote Control
• Behavior change: auto-archive-on-disconnect worked previously, stopped at some

point (exact version unknown)