refactor: remove setDefaultRequestHandler, use replaceRequestHandler

setDefaultRequestHandler was an untracked handler registration that
could silently overwrite user-set handlers if called after on* setters.
replaceRequestHandler serves the same purpose (allows re-registration)
without the silent-overwrite risk.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ochafik

src/app-bridge.ts

@@ -372,7 +372,7 @@ export class AppBridge extends ProtocolWithEvents<
 
     // Default handler for requestDisplayMode - returns current mode from host context.
     // Hosts can override this by setting bridge.onrequestdisplaymode = ...
-    this.setDefaultRequestHandler(
+    this.replaceRequestHandler(
       McpUiRequestDisplayModeRequestSchema,
       (request) => {
         const currentMode = this._hostContext.displayMode ?? "inline";

src/app.ts

@@ -415,9 +415,9 @@ export class App extends ProtocolWithEvents<
     }
     this._toolHandlersInitialized = true;
 
-    // Register via setDefaultRequestHandler so users can still override with
+    // Register via replaceRequestHandler so users can still override with
     // their own oncalltool/onlisttools after calling registerTool.
-    this.setDefaultRequestHandler(
+    this.replaceRequestHandler(
       CallToolRequestSchema,
       async (request, extra) => {
         const tool = this._registeredTools[request.params.name];
@@ -427,7 +427,7 @@ export class App extends ProtocolWithEvents<
         return (tool.handler as any)(request.params.arguments as any, extra);
       },
     );
-    this.setDefaultRequestHandler(ListToolsRequestSchema, async () => {
+    this.replaceRequestHandler(ListToolsRequestSchema, async () => {
       const tools: Tool[] = Object.entries(this._registeredTools)
         .filter(([_, tool]) => tool.enabled)
         .map(([name, tool]) => {

src/events.ts

@@ -188,19 +188,6 @@ export abstract class ProtocolWithEvents<
 
   // ── Handler registration with double-set protection ─────────────────
 
-  /**
-   * Register a request handler without tracking it. Subclass constructors
-   * use this for overridable defaults — a later `setRequestHandler` call
-   * (or `on*` setter) for the same method will succeed, replacing the
-   * default.
-   */
-  protected setDefaultRequestHandler: Protocol<
-    SendRequestT,
-    SendNotificationT,
-    SendResultT
-  >["setRequestHandler"] = (schema, handler) =>
-    super.setRequestHandler(schema, handler);
-
   // The two overrides below are arrow-function class fields rather than
   // prototype methods so that Protocol's constructor — which registers its
   // own ping/cancelled/progress handlers via `this.setRequestHandler`