Import march-2020-03-10 from private repo (scrubbed 2026-05-27)

Targets Rec Room 2020.03.10 client (also serves 2020.03.06).

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 dorknet-clientpatch-{key}.zip
  for v1-march-* Release uploads.
- .github/workflows/release.yml — on tag push publishes both
  dorknet-server-march_2020_03_10-win-x64.zip and
  dorknet-clientpatch-march_2020_03_10.zip as Release assets.

Same scrub rules as december; tools/build-patcher-zip.ps1 added to
the maintainer-side allow-list so it survives.

DorkNet.Server/Services/RoomBlobNormalizerService.cs

@@ -0,0 +1,63 @@
+using Google.Protobuf;
+using RecRoom.Protobuf2020;
+
+namespace DorkNet.Server.Services;
+
+/// <summary>
+/// Round-trips an uploaded <c>.room</c> protobuf blob through the
+/// 2020.03.06 client's full <c>PersistedRoomData</c> schema (generated
+/// at build time from <c>Protos/recroom_2020.proto</c>, which
+/// <c>tools/gen-proto-from-decompiled.py</c> produces by scanning
+/// <c>Cpp2IL_CS/.../RecRoom/Protobuf/*.cs</c>).
+///
+/// Why: newer Rec Room clients sometimes serialize PersistedRoomData
+/// with redundant default-zero fields, packed/unpacked variants the
+/// 2020 reader doesn't tolerate, or other non-canonical encodings.
+/// The 2020 watch's stricter <c>Google.Protobuf.MessageParser</c>
+/// then throws "Error attempting to parse room data stream" on
+/// download. Re-serialising via the 2020 schema strips redundant
+/// encodings and emits canonical proto3 wire format that the watch
+/// accepts.
+///
+/// On parse failure we hand the original bytes back unchanged — better
+/// to upload a blob that MAY work than to drop the user's content.
+/// Callers (the admin import endpoint) log the outcome.
+/// </summary>
+public sealed class RoomBlobNormalizerService(ILogger<RoomBlobNormalizerService> logger)
+{
+    public sealed record Result(byte[] Bytes, bool Normalized, int InputBytes, int OutputBytes, string? Error);
+
+    public Result Normalize(byte[] input)
+    {
+        if (input is null || input.Length == 0)
+            return new Result(Array.Empty<byte>(), false, 0, 0, "empty_input");
+
+        try
+        {
+            // Parse with the FULL 2020 schema. proto3 silently keeps
+            // unknown fields, so even if the input has fields the
+            // generated 2020 schema doesn't know about, they survive
+            // the round-trip.
+            var msg = PersistedRoomData.Parser.ParseFrom(input);
+            var output = msg.ToByteArray();
+            logger.LogInformation(
+                "[normalize] parse OK, in={In:N0} bytes, out={Out:N0} bytes ({Pct:F2}%)",
+                input.Length, output.Length, (double)output.Length / input.Length * 100);
+            return new Result(output, true, input.Length, output.Length, null);
+        }
+        catch (InvalidProtocolBufferException ex)
+        {
+            logger.LogWarning(
+                "[normalize] parse FAIL ({Bytes:N0} bytes): {Message} — passing original bytes through",
+                input.Length, ex.Message);
+            return new Result(input, false, input.Length, input.Length, ex.Message);
+        }
+        catch (Exception ex)
+        {
+            logger.LogWarning(ex,
+                "[normalize] unexpected exception ({Bytes:N0} bytes) — passing original bytes through",
+                input.Length);
+            return new Result(input, false, input.Length, input.Length, ex.Message);
+        }
+    }
+}