feat(browser): stream bounded live session updates (#26)

src/FinalFactory.Rendezvous.Contracts/Http/SessionContracts.cs

@@ -140,6 +140,10 @@ public sealed class UpdateSessionRequest
     [JsonRequired]
     public string LeaseToken { get; set; } = string.Empty;
 
+    public RegionId? RegionId { get; set; }
+    public uint? ProtocolVersion { get; set; }
+    public ListingVisibility? Visibility { get; set; }
+
     [JsonRequired]
     public string BuildVersion { get; set; } = string.Empty;
 
@@ -194,6 +198,32 @@ public sealed class BrowseSessionsResponse
     public List<SessionListing> Items { get; set; } = [];
 
     public string? NextCursor { get; set; }
+
+    [JsonRequired]
+    public string StreamCursor { get; set; } = string.Empty;
+}
+
+public enum SessionStreamEventKind
+{
+    SessionUpsert = 1,
+    SessionRemove = 2,
+    Reset = 3,
+    Keepalive = 4,
+}
+
+public sealed class SessionStreamEvent
+{
+    [JsonRequired]
+    public int ContractVersion { get; set; } = ContractLimits.ContractVersion;
+
+    [JsonRequired]
+    public SessionStreamEventKind Kind { get; set; }
+
+    [JsonRequired]
+    public string Cursor { get; set; } = string.Empty;
+
+    public SessionListing? Session { get; set; }
+    public SessionListingId? ListingId { get; set; }
 }
 
 public sealed class GetSessionResponse