docs: standardize UI terminology to use "view" consistently (#325)

* docs: standardize UI terminology to use "view" consistently

Replaces "widget" and "Guest UI" terminology with "view" across
the codebase as decided in the community survey.

This change updates:
- Specification document
- SDK source code and JSDoc comments
- Example servers and documentation
- Plugin documentation and skills

Closes #71

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

examples/threejs-server/src/mcp-app-wrapper.tsx

@@ -1,8 +1,8 @@
 /**
- * Three.js Widget - MCP App Wrapper
+ * Three.js view - MCP App Wrapper
  *
  * Generic wrapper that handles MCP App connection and passes all relevant
- * props to the actual widget component.
+ * props to the actual view component.
  */
 import type { App, McpUiHostContext } from "@modelcontextprotocol/ext-apps";
 import { useApp, useHostStyles } from "@modelcontextprotocol/ext-apps/react";
@@ -17,10 +17,10 @@ import "./global.css";
 // =============================================================================
 
 /**
- * Props passed to the widget component.
- * This interface can be reused for other widgets.
+ * Props passed to the view component.
+ * This interface can be reused for other views.
  */
-export interface WidgetProps<TToolInput = Record<string, unknown>> {
+export interface ViewProps<TToolInput = Record<string, unknown>> {
   /** Complete tool input (after streaming finishes) */
   toolInputs: TToolInput | null;
   /** Partial tool input (during streaming) */
@@ -55,7 +55,7 @@ function McpAppWrapper() {
   const [hostContext, setHostContext] = useState<McpUiHostContext | null>(null);
 
   const { app, error } = useApp({
-    appInfo: { name: "Three.js Widget", version: "1.0.0" },
+    appInfo: { name: "Three.js View", version: "1.0.0" },
     capabilities: {},
     onAppCreated: (app) => {
       // Complete tool input (streaming finished)