feat: add hot-pluggable language shell UI system

product-source/hololake-platform/docs/ABSTRACTIONS.md

@@ -1,5 +1,17 @@
 # Abstractions
 
+## `HoloLakeUiPlugin`
+
+A versioned, declarative presentation package for one host-owned semantic surface. It contains a manifest,
+safe `--hl-world-*` tokens, and a layout tree. `validateUiPlugin` is the authority at the renderer boundary;
+`createUiPluginRuntime` provides atomic activation, subscriptions, and last-known-good rollback.
+
+## `LanguageShellBridge`
+
+The narrow behavior boundary supplied by the host to a UI package renderer. Version 1 exposes goal submit
+and one reality-boundary answer; evidence expansion remains local presentation state. The bridge never gives
+the UI package direct repository, node, model, credential, permission, or deployment access.
+
 Key abstractions and domain models in Tolaria.
 
 ## Design Philosophy