feat: presence from Pulse — heartbeat flag, all-realms friends lookup, drop ONLY_SDK7

[mikhail-dcl]

Not verified in an editor — required before review

This branch was written in a sparse checkout without a Unity editor: nothing here has been
compiled and no test has been run. Before review, please

• let CI (or a local editor) compile Explorer/ and run the edit-mode suite,
• confirm the four new .cs.meta files import cleanly (they were hand-written with fresh GUIDs
  because *.meta is outside this checkout's sparse set — the editor may want to re-serialize them),
• play-mode verify the heartbeat flag: with archipelago-heartbeats served as false, the island
  room stays connected, keeps receiving island_changed, and reconnects after a socket drop (ws-connector
  pings idle sockets itself since the server-side WP3a change),
• play-mode verify the forced fresh handshake with the flag off (the path a socket drop never
  reaches): make the cached connection string fail three times in a row so
  ArchipelagoIslandRoom.ForceFreshIslandAssignmentAsync runs, and confirm an island_changed still
  arrives. This works because ws-connector publishes peer.{address}.connect after every handshake and
  comms-gatekeeper re-emits the peer's current island assignment on it — see the rollout note below.

Rollout ordering — this client release must ship last

The kill switch removes the client Heartbeat, and until recently a fresh peer session got its island
assignment only after one. Two server changes replace that: ws-connector publishes
peer.{address}.connect after every handshake, and comms-gatekeeper re-emits the current
island_changed on that subject. Both must be deployed before a client build carrying this flag
reaches production (rollout step 7 after steps 5–6), and archipelago-heartbeats must stay unset (or
true) until they are. No client-side change is needed for it.

What this does

Server side (already shipped): GET …/comms/peers?id=… searches all realms and every peer carries
"realm" ("cozyfarm.dcl.eth" for a world, "main" for Genesis City); ws-connector pings idle sockets.

1. Heartbeats behind a server-controlled flag. New feature flag archipelago-heartbeats
(FeatureFlagsStrings.ARCHIPELAGO_HEARTBEATS / FeatureId.ArchipelagoHeartbeats), read in
FeaturesRegistry through FeatureFlagsConfiguration.IsEnabledUnlessKilled — a default of on, so a
deploy that changes no flag, and a client whose flag fetch failed, behave exactly as today.

The flag is read in exactly one place: ArchipelagoIslandRoom.SendHeartbeatIfEnabledAsync, which the
cycle step calls after its reconnect check. With the flag off nothing else runs — no position read, no
thread-pool hop, no call into the sign flow — so no Heartbeat reaches the socket.
LiveConnectionArchipelagoSignFlow stays a dumb transport that always sends what it is asked for, so a
success result from it always means the position really reached archipelago. The socket, the sign flow
and island_changed handling are untouched.

Rollback: serve archipelago-heartbeats: true (or nothing at all) — today's behaviour.

2. One all-realms friends lookup. OnlinePlayersJsonDtoConverter maps a peer's realm into
OnlineUserData.worldName when it ends with .dcl.eth (case-insensitive suffix, name kept verbatim),
and leaves it unset otherwise (main, another realm, absent field). WorldInfoOnlineUsersProviderDecorator,
DecentralandUrl.RemotePeersWorld, its DecentralandUrlsSource case and its GatewayUrlsSource entry
are deleted, along with the dead [JsonProperty("world"/"wallet")] mapping on OnlineUserData that only
the decorator's connected-world body ever used.

To be accurate about the win: this is not an N-per-friend saving. Every call site
(FriendListSectionUtilities, FriendSectionController, FriendsSectionDoubleCollectionController,
PassportController, CommunityPlayerEntryContextMenu, GenericUserProfileContextMenuController)
passes a one-element buffer with a single address, so the retired decorator cost one extra
/wallet/:wallet/connected-world request per jump-in click (1+1, not 1+N). What is gone is that second
request and its dependency on worlds-content-server. The contract caps ?id= at 200 ids per request
(201+ answers 400 {"ok":false,"error":"too many ids (max 200)"}), so a future caller that does batch a
real friend list has to chunk. The unfiltered GetAsync(ct) (map hot-user markers) is unchanged and
keeps main-realm semantics through the 308.

3. ONLY_SDK7 housekeeping. The platform is SDK7-only and the places API ignores only_sdk7, so the
URLParameter and every onlySdk7 parameter/argument are gone — the query parameter is no longer sent
at all. The Places UI toggle is deliberately left as it is: PlacesFilters.SDKVersion still exists, is
still settable, and is still emitted to analytics as an applied filter (PlacesAnalytics), while no
longer reaching the request. Removing the control needs a prefab edit, which is outside this sparse
checkout — please open a follow-up ticket for the UI + analytics removal.

Not touched: MainSceneLoader.IsLIvekitDeadAsync (ArchipelagoStatus + GatekeeperStatus health
gate) and GoToChatCommand /goto crowd (ArchipelagoHotScenes).

Tests (written, not run)

• Explorer/Assets/DCL/Multiplayer/Connections/Archipelago/Tests/ArchipelagoHeartbeatKillSwitchShould.cs
  — the kill switch's only guarantee. Drives ArchipelagoIslandRoom over the real
  LiveConnectionArchipelagoSignFlow and asserts at IArchipelagoLiveConnection, the socket
  abstraction: flag served false → nothing sent at all; flag served true, and no flag resolved
  (the rollback default) → exactly one ClientPacket whose MessageCase is Heartbeat, carrying the
  player's position. Deleting the guard or hoisting its flag read into a constructor fails here.
• Explorer/Assets/DCL/FeatureFlags/Tests/FeaturesRegistryArchipelagoHeartbeatsShould.cs — flag absent →
  enabled; served true → enabled; served false → disabled; plus the kill-switch read itself.
• Explorer/Assets/DCL/Tests/Editor/OnlinePlayersJsonDtoConverterShould.cs — over the contract golden
  (Explorer/TestResources/iteration-2/http/peers-by-id.json, byte-identical to the fixture pack, pinned
  eol=lf in .gitattributes because the pack digests it): cozyfarm.dcl.eth → worldName, main →
  none, plus the realm→world-name cases (absent / null / empty / non-world ENS / mixed-case suffix).
• Explorer/Assets/DCL/Tests/Editor/ArchipelagoHttpOnlineUsersProviderShould.cs — edit-mode with a
  substituted IWebRequestController (play-mode would need a live archipelago). The stubbed response is
  the golden body itself (id, lastPing, parcel, realm included), decoded by the real
  converter: three ids produce one ?id=&id=&id= request, no request URL contains connected-world,
  and the peer in a world comes back with the world name from that single call.
• DecentralandUrlsSourceShould — RemotePeers resolves on a custom base domain.

Run them in the editor: Window > General > Test Runner > EditMode (or the CI edit-mode job), which runs
all four fixtures — none of them carries a [Category], so the workflow's -testCategory "!Performance"
filter includes them.

Review round 1 — what changed

finding	fix
F1 major — the kill switch had no test	ArchipelagoHeartbeatKillSwitchShould (above). The flag read moved out of the protected cycle step into internal ArchipelagoIslandRoom.SendHeartbeatIfEnabledAsync so it can be driven from DCL.EditMode.Tests, which DCL.Multiplayer already grants InternalsVisibleTo.
F2 major — the fresh-handshake recovery relied on "after the next heartbeat"	Server-side gap, fixed server-side (ws-connector peer.{address}.connect + comms-gatekeeper re-emit). The stale doc comment on ForceFreshIslandAssignmentAsync is corrected; rollout ordering and the extra play-mode check are stated above. No client logic added.
F3 — IsEnabled(id, defaultWhenAbsent) was one keyword from its opposite	Renamed to IsEnabledUnlessKilled(id). No twin to mis-copy, and IsEnabled(id, null) is no longer ambiguous.
F4 — the provider test did not consume the golden	It now deserializes the golden body (shared with the converter fixture) instead of a hand-rolled two-field response.
F5 — "one call for all friends" oversold the win	Corrected here and in the report; the fixture doc records the 1+1 reality and the 200-id cap; AskForEveryFriendInOneRequest → AskForEveryRequestedIdInOneRequest.
F6 — the sign flow's second guard reported success without sending	Removed. One guard, in the room; the sign flow is honest about what it sent.
F7 — dead [JsonProperty] on OnlineUserData	Removed.
F8 — the Places SDK filter is inert but still shown and still reported	Left as is (prefab edit needed); called out above for a follow-up ticket.
F9 — ResolveNoPerFriendConnectedWorldLookup was vacuous	Dropped. The enum member's deletion is compiler-enforced, and the request-count assertion in the provider fixture is what actually catches a returning per-friend lookup.

Flag semantics: archipelago-heartbeats is read once at launch (no live refresh). After the flag is disabled server-side, sessions already running keep sending heartbeats until they restart, so the ws-connector intake (HEARTBEAT_FORWARDING_ENABLED) must stay on until sessions have cycled (allow ≥ 24 h after the ramp).

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