Import december-2020-12-18 from private repo (scrubbed 2026-05-27)

Targets Rec Room 2020.12.18 client.

Re-import after adding:
- DorkNet.ClientMod/dorknet-clientmod.json.template — config schema
  the launcher's manifest-driven patcher renders into UserData/.
- tools/build-patcher-zip.ps1 — produces the dorknet-clientpatch-{key}.zip
  Release asset the launcher fetches.
- .github/workflows/release.yml — auto-publishes both Release assets
  on v1-december-* tag push.

Scrubbed via maintainer-side scrub-for-public.ps1: same drop rules as
the prior import, plus build-patcher-zip.ps1 added to the tools/
allow-list so it survives the scrub.

DorkNet.Server/Data/Entities/ChatThreadEntity.cs

@@ -0,0 +1,31 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace DorkNet.Server.Data.Entities;
+
+/// <summary>
+/// Per-thread metadata for chat: name (for group chats), creator, and
+/// timestamps. Rows here are sparse — a two-person DM doesn't need
+/// one unless the players want a custom thread name. Group chats
+/// always have a row so the member set + name are persisted.
+/// </summary>
+public class ChatThreadEntity
+{
+    public long Id { get; set; }
+
+    /// <summary>Canonical thread key (matches <c>ChatMessageEntity.ThreadKey</c>).
+    /// Format: <c>dm:&lt;low&gt;:&lt;high&gt;</c> for DMs,
+    /// <c>group:&lt;guid&gt;</c> for group chats, <c>room:&lt;id&gt;</c> for room-wide.</summary>
+    [MaxLength(96)]
+    public string ThreadKey { get; set; } = string.Empty;
+
+    /// <summary>Optional custom name. DMs default to empty (watch renders
+    /// "Chat with &lt;username&gt;" client-side); group chats persist a
+    /// name set via <c>PUT thread/{id}/rename</c>.</summary>
+    [MaxLength(128)]
+    public string Name { get; set; } = string.Empty;
+
+    public long CreatorPlayerId { get; set; }
+
+    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+    public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
+}