Show what conversation analysis did under each Chat message

Applied messages get a quiet line naming the card they changed, failed
analysis shows a warning line with Retry, and the always-visible code icon
becomes a hover-revealed Details action. The details popover animates,
leads with the outcome, and keeps model and policy data behind a closed
Diagnostics disclosure. The popover body loads on first use.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>