Add a "🗑 Purge stale contacts…" action at the foot of the Contacts list. It
offers an age ladder (1 week → 1 year, plus a never-heard bucket), each rung
showing a live count of how many contacts it would sweep, so the impact is
visible before choosing; the pick is gated behind a typed "delete" confirm.
A purge deletes each contact from the device table (new Device.remove_contact,
over the meshcore remove_contact command) and forgets it from the cross-session
contact store so a firmware-less bridge doesn't merge it back — but only the
contact is dropped: each node's reception history in MeshTerm is untouched, and
our own pinned node is never a candidate. The contacts cache is invalidated and
the list rebuilt so swept contacts are gone from it.
ContactListScreen gains a `tail` param (symmetric to `lead`) for the action and
Back rows; age bucketing (stale_past / never_heard) is factored out pure and
tested, alongside MockDevice.remove_contact and the screen's tail composition.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Jean-Pierre MartineauandClaude Opus 4.8
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