Put a user message's copy button beside its timestamp

The copy button sat on its own row above the group's time, costing a
line of vertical space for nothing. It now shares that row, left of the
timestamp, the way a bot message's actions already do. A file-only
message leaves no gap: only messages with text get a button, picked by
copyableMessages.

src/pages/admin/bots/[bot_id]/(utils)/copyable-messages.test.ts

@@ -0,0 +1,27 @@
+import { describe, expect, test } from "bun:test";
+import type { BotMessageWithAttachments } from "@/src/types";
+import copyableMessages from "./copyable-messages";
+
+function message(text?: string): BotMessageWithAttachments {
+    return { id: 1, author: "user", text } as BotMessageWithAttachments;
+}
+
+describe("copyableMessages", () => {
+    test("keeps the messages that have text", () => {
+        const kept = copyableMessages({
+            messages: [message("hello"), message(undefined), message("hi")],
+        });
+
+        expect(kept.map((one) => one.text)).toEqual(["hello", "hi"]);
+    });
+
+    test("drops text that is only whitespace", () => {
+        expect(copyableMessages({ messages: [message("   ")] })).toEqual([]);
+    });
+
+    test("a group with no text has nothing to copy", () => {
+        expect(copyableMessages({ messages: [message(), message()] })).toEqual(
+            [],
+        );
+    });
+});

src/pages/admin/bots/[bot_id]/(utils)/copyable-messages.ts

@@ -0,0 +1,14 @@
+import type { BotMessageWithAttachments } from "@/src/types";
+
+/**
+ * The messages of a group that can be copied: a file-only message has no
+ * text, and its copy button renders nothing, so it would only leave a
+ * gap in the row.
+ */
+export default function copyableMessages({
+    messages,
+}: {
+    messages: BotMessageWithAttachments[];
+}): BotMessageWithAttachments[] {
+    return messages.filter((message) => Boolean(message.text?.trim()));
+}