feat: add web search tool with reranking support

Integrates SearXNG web search as a tool available during chat when the
agent has search enabled. Supports optional reranking of results via a
configurable reranking model. Replaces Python subprocess evaluation with
@pydantic/monty WASM runtime. Introduces stable tool call ID mapping to
avoid exposing provider-native IDs to the database.

app/composables/useAgents.ts

@@ -123,9 +123,9 @@ export const useAgents = async () => {
                     a.id === id ? agent : a
                 );
             },
-            async onResponse() {
-                await refresh();
-            }
+            // async onResponse() {
+            //     await refresh();
+            // }
         });
     }
 
@@ -166,7 +166,7 @@ export const useAgents = async () => {
             body: topic,
             onRequest() {
                 agents.value = agents.value.map(a =>
-                    a.id === agentId ? { ...a, topics: [{ ...topic, createdAt: new Date() }, ...a.topics] } : a
+                    a.id === agentId ? { ...a, topics: [{ ...topic, createdAt: new Date() }, ...a.topics] } as AgentWithTopics : a
                 );
             },
             onResponseError() {