The original key 'pinPeerName' from #14984 is ambiguous: a fresh
reader can't tell whether it pins the user peer or the AI peer from
the name alone. The resolver only ever pins the user-side
(_resolve_user_peer_id short-circuits when pin_peer_name is true; the
AI peer is already pinned by construction via aiPeer).
Add 'pinUserPeer' as the canonical alias. Both keys land on the
same internal pin_peer_name field; precedence is host pinUserPeer →
host pinPeerName → root pinUserPeer → root pinPeerName → default.
Host-level always beats root-level regardless of alias, so a host
block can still explicitly disable a root-level pin even via the new
key.
Make _resolve_bool variadic so it can express the four-value
precedence chain. All existing callers pass two positional args +
default keyword, which the new signature accepts unchanged.
Internal var name (pin_peer_name) stays the same to keep the
cherry-picked #27371 commits clean and avoid a noisy rename diff.
3cf5e8225d