feat: Add ProtoDumper for runtime Google.Protobuf schema extraction and decoding

DorkNet.ProtoDumper/README.md

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+# DorkNet ProtoDumper
+
+Runtime extractor for Rec Room's Google.Protobuf schema (room save /
+creation / circuits data model). Produces clean `.proto` files for any
+client build — including obfuscated ones like 2023.03.21 where static
+reconstruction from `global-metadata.dat` is unreliable (the descriptor
+base64 is split into scattered string-literal chunks whose concat order
+only lives in IL).
+
+At runtime every `FileDescriptor` still carries its original,
+un-obfuscated `FileDescriptorProto` (real message names, field names,
+numbers and types intact). The catch: Rec Room builds these descriptors
+**lazily and in a specific dependency order** as content loads. Trying to
+force-build them by reading a message type's static descriptor out of
+order throws inside the type's static constructor, and the failure is
+cached — *poisoning* the type (and crashing the client). So this mod does
+**not** enumerate types.
+
+Instead it Harmony-postfixes the one library method every generated cctor
+funnels through —
+`Google.Protobuf.Reflection.FileDescriptor.BuildFrom` /
+`.FromGeneratedCode` — and records each descriptor as the game builds it.
+Completely passive: **play the client through the content you care about**
+and every descriptor that loads is captured.
+
+## Pipeline
+
+1. **Build the mod**
+
+   ```sh
+   dotnet build DorkNet.ProtoDumper/DorkNet.ProtoDumper.csproj -c Release
+   ```
+
+   Output: `DorkNet.ProtoDumper/bin/Release/DorkNet.ProtoDumper.dll`.
+
+2. **Run it on a *runnable* 2023.03.21 client (MelonLoader 0.6.6)**
+
+   > The `GameAssembly.dll` + `il2cpp_data`-only copy under
+   > `Recnet-old/dist/RecRoom-2023.03.21-il2cpp/…/staging/` is an
+   > **offline-analysis payload, not a runnable build**. Use a full build
+   > with the exe + UnityPlayer + MelonLoader (e.g. the devdork package).
+
+   - Drop `DorkNet.ProtoDumper.dll` into `<RecRoom>\Mods\`. On launch it
+     installs the descriptor-build hooks (see `dump.log` / MelonLoader
+     console for "installed N descriptor-build hooks").
+   - **Log in and play through the content whose schema you want:** your
+     dorm, a created room, the Maker Pen, and a circuits (CV2) board. Each
+     subsystem builds its protos the first time it loads. Descriptors are
+     captured the instant they build — no scene/timer scanning, nothing is
+     force-built, so the client stays stable.
+   - Output appears under `<RecRoom>\DorkNet-ProtoDump\` and is flushed to
+     disk ~1 s after new descriptors load, and again on quit:
+     - `manifest.tsv`   — `<proto path>\t<base64>` per file
+     - `files\*.b64`    — same, one file each
+     - `dump.log`       — running capture count
+
+3. **Decode to .proto**
+
+   ```sh
+   pip install protobuf
+   python DorkNet.ProtoDumper/decode_dump.py <path>/manifest.tsv proto_out
+   ```
+
+   Emits one `.proto` per descriptor under `proto_out/`, plus a combined
+   `proto_out/recroom_2023.proto` (every rec_room/circuits message in one
+   file) for an easy diff against
+   `DorkNet.Server/Protos/recroom_2020.proto`.
+
+## Notes
+
+- No game DLLs are referenced at compile time. `FileDescriptor` is the
+  Google.Protobuf *library* type (not obfuscated); it's reached by its
+  original name with the Il2Cpp namespace-prefix fallback, and its members
+  are read via reflection. The same DLL works across builds and stays clean
+  of derivative game code.
+- The only Harmony patches are the two read-only descriptor-build
+  postfixes above — safe to run alongside (or without) `DorkNet.ClientMod`.
+- The descriptor base64 is the same `FileDescriptorProto` wire format
+  Google's own tooling emits, so `decode_dump.py` (or `protoc
+  --decode=google.protobuf.FileDescriptorProto descriptor.proto`) reads it
+  directly.