[Bug] - Message datetime uses render time even when a saved timestamp is supplied #938

Description

When a saved timestamp is passed to Message, the visible timestamp and the message section's accessible label correctly use the supplied string. However, the underlying <time datetime="..."> attribute still contains the time of rendering. It also changes on subsequent renders.

This makes the machine-readable timestamp disagree with the displayed message time. Consumers can supply timestamp?: string, but cannot supply the actual date to the nested PatternFly Timestamp component.

The implementation creates const date = new Date() during rendering and uses <Timestamp date={date}>{timestamp}</Timestamp>:
https://github.com/patternfly/chatbot/blob/aca7848d3212003a20ebcd916217e9d29c9862e6/packages/module/src/Message/Message.tsx

Expected: Consumers should be able to provide the saved message instant so that both the displayed timestamp and the HTML datetime describe that instant and remain stable across rerenders.

Actual: Supplying timestamp fixes the displayed text, but datetime continues to describe render time.

Related reports #448 and #299, and documentation PR #302, explain that applications must supply persistent timestamps. This report concerns the remaining HTML datetime mismatch even after following that guidance.

A possible backward-compatible solution is an optional date prop forwarded to the native Timestamp, while retaining the existing display-string prop and default behavior. The API shape is open for discussion; localized display strings should not need to be parsed to recover the date.

Steps to Reproduce

1. Render the example below using @patternfly/chatbot.
2. Inspect the <time> element inside the message in browser developer tools.
3. Notice that its text is the supplied historical timestamp, while its datetime attribute is the current render time rather than 2025-01-15T10:00:00.000Z.
4. Wait a few seconds, then click Rerender.
5. Inspect the same element again: the displayed text remains unchanged, but datetime has advanced.

Data/JSON Context (if applicable)

import { useState } from 'react';
import { Message } from '@patternfly/chatbot';

export default function TimestampReproduction() {
  const [renderCount, setRenderCount] = useState(0);

  return (
    <>
      <button onClick={() => setRenderCount((count) => count + 1)}>
        Rerender ({renderCount})
      </button>
      <Message
        role="user"
        name="You"
        content="A saved message"
        timestamp="2025-01-15 10:00:00 UTC"
      />
    </>
  );
}

Environment

• PatternFly Chatbot: 6.7.1
• PatternFly React Core: 6.6.1
• React: 19.3.0
• Browser: Chromium (exact version not recorded)
• Viewport: observed in desktop chat; the date is generated in the component independently of layout
• The same timestamp implementation is present in the linked upstream source revision.

Screenshots or Logs

DOM inspection of a saved conversation showed the following values (displayed text was in Asia/Kolkata, UTC+05:30):

The supplied visible timestamp remained correct; the HTML attribute represented the later render time.