#7940: fix(googlechat): add messageReplyOption for proper thread replies

Add REPLY_MESSAGE_FALLBACK_TO_NEW_THREAD query parameter to ensure bot replies are posted within the existing thread instead of creating new messages in the main space. This fixes the issue where bot responses appeared outside of threads when users messaged within a Google Chat thread context. <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR updates the Google Chat message send endpoint to include the `messageReplyOption=REPLY_MESSAGE_FALLBACK_TO_NEW_THREAD` query parameter when posting messages, aiming to keep bot replies within an existing thread rather than creating a new top-level message in the space. Change is localized to `extensions/googlechat/src/api.ts` in `sendGoogleChatMessage`, which is used by the Google Chat channel implementation when sending text/media replies. <h3>Confidence Score: 4/5</h3> - This PR looks safe to merge; it’s a small behavioral change confined to Google Chat message sending. - The change is a single query parameter addition and should not affect other endpoints, but it does slightly alter message routing semantics for all sends, so it’s worth ensuring this is desired for non-threaded posts as well. - extensions/googlechat/src/api.ts <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} <!-- /greptile_comment -->