Where a server is, on the public instance API

/api/privapub/v1/instances/:host gains `geo`, the public projection of a
server's place already decided for public server locations
(PublicGeo.Project): city, coordinates and network for servers reporting
at least 10 users and not behind a CDN, the country otherwise, the CDN's
name for a CDN-fronted one, with DB-IP's attribution. `?host[]=`
answers up to 40 servers at once, and this server describes itself:
its host's address located once a day (SelfLocation), or
Statistics:Geo:Self when the owner sets it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

docs/INTEROP.md

@@ -1,4 +1,4 @@
-# Interop: what every peer sends, what it expects, and what PrivaPub still drops
+# Interop: what every peer sends, what it expects, and what PrivaPub still drops
 
 Research as of **2026-10-01**: the platforms' source on their default branches, live ActivityPub fetches from large
 instances, release notes and the FEP repository. Version numbers are what was current that day. Claims the
@@ -807,7 +807,9 @@ a remote host.
 
 `GET /api/privapub/v1/instances/:host` returns cached NodeInfo (`metadata` extras: Misskey `themeColor`/`maxNoteTextLength`,
 Pleroma `features[]`/`federation.mrf_policies`), the instance API's icon and description, the delivery health our
-circuit breaker sees, and which signature scheme worked.
+circuit breaker sees, and which signature scheme worked. Its `geo` is the public projection of where the server is
+(`precision` `city`, `country` or `cdn`, ROADMAP owner decision on server locations); `?host[]=` answers up to 40 at
+once, and this server describes itself the same way.
 
 `software.name` → family, for display: