fix: address all Gemini code review comments

- LearningAgent: replace `BaseAgent` (deleted on main) with `DurableObject<Env>`
  which provides properly typed `this.env` access
- LearningAgent: remove `__proto__.__proto__` brittle prototype chain access,
  use simple 404 fallback instead
- LearningAgent: typed `LearningEnv` interface for AI and VECTORIZE_INDEX
  bindings (already applied in previous commit)
- BaseAgent `super.fetch as Function` comments: N/A, file removed on main
- JulesOverseer `__proto__.__proto__` comment: N/A, already uses `super.fetch()`
  on main's version

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: jmbish04

src/backend/src/ai/agents/LearningAgent.ts

@@ -14,7 +14,7 @@
  * @module AI/Agents/LearningAgent
  */
 
-import { BaseAgent } from "./base/BaseAgent";
+import { DurableObject } from "cloudflare:workers";
 import { getDb } from "@db";
 import {
   learningAiInsights,
@@ -84,10 +84,7 @@ const STANDARD_VIOLATION_PATTERNS: RegExp[] = [
 // LearningAgent
 // ---------------------------------------------------------------------------
 
-export class LearningAgent extends BaseAgent {
-  constructor(state: DurableObjectState, env: Env) {
-    super(state, env);
-  }
+export class LearningAgent extends DurableObject<Env> {
 
   async fetch(request: Request): Promise<Response> {
     const url = new URL(request.url);
@@ -138,8 +135,7 @@ export class LearningAgent extends BaseAgent {
       });
     }
 
-    // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    return (this as any).__proto__.__proto__.fetch?.call(this, request) ?? new Response('Not found', { status: 404 });
+    return new Response('Not found', { status: 404 });
   }
 
   // ---------------------------------------------------------------------------