fix(chat-platform): keep the page block's comment vendor-neutral - #2464

🟢 Confidence 10/10 · safe to merge. Two-line comment reword with no code change; the vendor-isolation scan's name list no longer matches the text at blocks.ts:162.
_{no findings · tests not needed · risk low}

Rewords the ChatPageBlock doc comment so it no longer names a chat vendor, letting the chat-platform vendor-isolation scan pass on main. Comment-only; safe to merge.

• ChatPageBlock doc comment no longer names a vendor, keeping the isolation scan green

_{58701ba · Reply "won't fix" to dismiss a finding, or mention @maple-review-bot to ask about one.}