Share a guide page with its preview, and past the password with a key
Share, in a guide's header, copies the page's address and shows the card it unfurls as in Slack, iMessage and email. For a guide with a password, Share can add a key to the link: the link then previews the page and opens it without the password for 30 days, and changing or removing the password ends every key. Under Theme docs, Link previews shows the cards as they stand, and Refresh previews gives every link's card a new address, so a chat app that kept an old card fetches the new one.
A link without a key behaves as before: a guide with a password previews with its name alone, whoever asks. The key is bound to the password, is good for one guide, and is never stored: it is worked out again from the password's hash each time a link is checked.
Cards now carry the guide's last change in their address, so a run also refreshes what chat apps show.
More in Theme documentation.