My solution was to write a quick AppleScript that marks the unread message in the folder [Gmail]/All Mail as read immediately on retrieval: Be sure to change Gmail IMAP to the name of your Google account. If you're unsure of the official name, add get accounts in the tell application section to find the official name. While this is far from an elegant solution, it could help until Apple and Google coordinate their efforts. If you have any suggestions to make this script more efficient, please share!
[robg adds: Although it's not stated in the hint submission, I believe the last step is to assign this script to run as a rule on all inbound Gmail messages...]

