Improve chat title generation and context compacting

test/app.test.js

@@ -752,9 +752,11 @@ test("chat memories are durable facts included in model payload", async () => {
 test("chat context summary rolls up older messages into future payloads", async () => {
     let replyCount = 0;
     let latestPayload = [];
+    let summaryModel = null;
     const modelService = {
         async generateReply(model, messagesPayload) {
             if (messagesPayload.some((message) => message.content.includes("Merge the previous summary"))) {
+                summaryModel = model;
                 return "Summary: user greeted the assistant and asked for continuity.";
             }
             latestPayload = messagesPayload;
@@ -810,6 +812,7 @@ test("chat context summary rolls up older messages into future payloads", async
 
     assert.ok(latestPayload.some((message) => message.role === "system" && message.content.includes("CONVERSATION SUMMARY")));
     assert.ok(latestPayload.some((message) => message.content.includes("user greeted the assistant")));
+    assert.equal(summaryModel, "nomic-embed-text:latest");
 
     await server.close();
 });