Vendor STS2MCP mod source and 0.4.0 release DLL

Full C# source of the kunology STS2MCP fork (McpMod HTTP bridge for
game state and actions) plus the prebuilt 194,560-byte release DLL and
its manifest. The rebuilt fork DLL from docs/research/03 is not saved;
rebuild from this source if the pinned 0.4.0 breaks on a game update.

vendor/STS2_MCP.json

@@ -0,0 +1,10 @@
+{
+  "id": "STS2_MCP",
+  "name": "STS2 MCP",
+  "author": "kunology",
+  "description": "MCP server bridge for Slay the Spire 2",
+  "version": "0.4.0",
+  "has_pck": false,
+  "has_dll": true,
+  "affects_gameplay": false
+}