[match] support a cluster of tachyon servers

apps/match/src/context.ts

@@ -53,17 +53,21 @@ export type Env = SharedHonoEnv & {
 	/** The Photon Chat application id. Optional; see {@link Env.PHOTON_REALTIME_APP_ID}. */
 	PHOTON_CHAT_APP_ID?: string
 	/**
-	 * The Tachyon voice server the client is handed as `voiceConnectionInfo` on
-	 * `GET /player/connection-info`, as `host:port` (e.g. `66.228.47.217:7777`).
-	 * Optional, and EMPTY when unset — no separate voice server. Not a secret (the
-	 * client receives it in the clear), so a plain var like the Photon ids.
+	 * The pool of Tachyon servers sessions are spread across — a COMMA-SEPARATED list of
+	 * `host:port` entries (e.g. `66.228.47.217:7777,66.228.47.217:7778,45.79.2.10:7777`).
+	 * One entry is a single server, which is the common case. Optional, and EMPTY when
+	 * unset — no separate voice server, and the connection info's voice fields stay empty.
+	 * Not a secret (the client receives it in the clear), so a plain var like the Photon
+	 * ids.
+	 *
+	 * A room instance is assigned one entry for its lifetime and every player in it is
+	 * handed that one, derived from the instance id rather than stored — see
+	 * `tachyonServerFor` in match.app.ts, which also explains what changing this list does
+	 * to sessions already running. The `voiceServerId` the client displays is GENERATED
+	 * from an entry's position (`tachyon-1`, `tachyon-2`, …), so the same address may be
+	 * listed twice to model two server slots on one box.
 	 */
 	TACHYON_HOST_PORT?: string
-	/**
-	 * The id of that voice server, handed to the client as `voiceServerId` (e.g.
-	 * `server-1`). Optional; see {@link Env.TACHYON_HOST_PORT} — set both or neither.
-	 */
-	TACHYON_NAME?: string
 	/**
 	 * The Photon region every session is pinned to — both the region named in the connection
 	 * info and the one stamped on every room instance, which must agree. Optional; unlike the