Add support for message history pagination, preserve scroll in rendering, and improve draft/message workflows.

browser-tests/conversation.html

@@ -0,0 +1,27 @@
+<!doctype html>
+<html lang="en">
+<meta charset="utf-8">
+<title>Conversation navigation regression tests</title>
+<h1>Conversation navigation regression tests</h1>
+<div id="testTitle"></div>
+<input id="testModel" aria-label="Model">
+<input id="chatSearchInput" aria-label="Search">
+<textarea id="msgInput" aria-label="Draft"></textarea>
+<div id="messages"></div>
+<pre id="results">Running...</pre>
+<script type="module">
+    import {registerConversationTests} from "/browser-tests/conversationCases.js";
+    const cases = [], results = [];
+    const assert = {
+        equal(actual, expected) { if (!Object.is(actual, expected)) throw new Error(`Expected ${expected}, received ${actual}`); },
+        deepEqual(actual, expected) { this.equal(JSON.stringify(actual), JSON.stringify(expected)); }
+    };
+    registerConversationTests((name, run) => cases.push({name, run}), assert);
+    for (const {name, run} of cases) {
+        try { await run(); results.push(`PASS ${name}`); }
+        catch (error) { results.push(`FAIL ${name}: ${error.stack}`); }
+    }
+    document.getElementById("results").textContent = results.join("\n");
+    document.title = `${results.filter(result => result.startsWith("PASS")).length}/${cases.length} navigation tests passed`;
+</script>
+</html>