Use this when the user asks to turn something from their memory into a
card, a shareable summary page, or a link they can share. Do not use it to
save a memory; use `save_memory` for that.

Creating is publishing: the card page and two share images are live on the
open web the moment this returns. The card is unlisted, so nobody finds it
without the address, but anyone holding the address can open it with no
login. It cannot be edited or taken down from here. Write it only from
memory the user can already read; the server never calls a model. Listing,
deleting, search visibility and filing tags for cards the user made are
handled by the user in the AiAkiv web console.

Limits, checked by the card service after it trims whitespace and drops
empty items: title up to 80 characters; 3 to 5 bullets of up to
120 characters each; conclusion up to 200 characters; source_count
an integer of 0 or more; up to 3 tags of up to 20 characters each; body
up to 30,000 characters. Title, bullets, conclusion and tags are single
lines; line breaks in them collapse to spaces.

Fitting the images: bullets share one fixed block of vertical space, so
their count and length trade against each other. A line holds about 31
Korean characters (Latin letters and spaces fit more) and each bullet gets
up to 3 lines, but when the total does not fit, every bullet is cut to
fewer lines and shortened with an ellipsis, so staying under 120 characters
is not enough. With a title of up to about 20 Korean characters and a
conclusion of up to about 30, three or four bullets of up to about 40
Korean characters each fit both images; with 5 bullets the last one
is left out of the wide image. The page always shows the full text. Aim to
fit on the first try: creating again makes a new card and leaves this one
published until the user deletes it.

Args:
    title: The card title, one line, up to 80 characters.
    bullets: 3 to 5 key points, one line each, up to 120 characters each.
    conclusion: A one-line conclusion, up to 200 characters.
    source_count: How many memories the card was written from. Defaults to 0.
    tags: Up to 3 search terms for the card, up to 20 characters each. They are drawn into the images and cannot be changed later. Defaults to none.
    body: Optional longer text shown on the page but not in the images, up to 30,000 characters of restricted markdown: paragraphs, `##` headings, `-` and `1.` lists, `>` quotes, inline and fenced code, bold, italic, http(s) links and `---`. Anything else shows as plain text.

Returns:
    On success `{notice, ok, app, key, url, og_url, square_url, fit?, ...}`.
    `notice` comes first and states what just became public and how to take
    it down; it is information the user needs to see. `url` is the card
    page; `og_url` and `square_url` are the share images. `fit`, present
    only when an image cut something, names the bullets that were shortened
    or left out and how much to shorten them. On failure
    `{error, message or hint, field?}` and no card was made: `invalid_card`
    names the field to fix, `quota_exceeded` carries the window, limit and
    used counts.