docs(headless): close K0 and activate K1

Pin the tested Windows/Linux portability boundary, exact rollback, dependency audit, and synchronized architecture and roadmap state before starting the production single-session host.

Co-authored-by: Codex <noreply@openai.com>

docs/architecture/acdream-architecture.md

@@ -245,6 +245,12 @@ src/
     -> Slice J complete; graphical and no-window hosts share one GameRuntime
     -> may reference Core, Core.Net, Content, and Plugin.Abstractions only
     -> must never reference App, UI, Silk.NET, OpenAL, Arch, or ImGui
+
+  AcDream.Headless/          Linux/Windows no-window production host
+    Program.cs               -> CLI entry only
+    Configuration/           -> strict versioned process/session config
+    -> references Runtime only; no presentation/backend package
+    -> K0 complete; K1 single-session host active
   
   AcDream.Plugin.Abstractions/  Layer 5: plugin interfaces
     IAcDreamPlugin.cs         -> done