The card message converter (shortcuts/im/convert_lib/card.go) previously
rendered a subset of card fields and had several mode-gated behaviors that
caused information to be silently dropped in concise mode. This PR audits
every element handler and brings the output up to full fidelity:
missing header fields are rendered, collapsible panels always expand, rich
element metadata (images, audio, video, overflow URLs, person names) is no
longer hidden behind cardModeDetailed, and several format bugs are fixed.
Change-Id: I422474ab6b7505e48ab5697793900df035be6e29
Interactive card messages (msg_type: interactive) can contain @user elements in their card
body. The json_attachment.at_users field stores resolved user info, but the user_id there is
the sender-side platform user_id — not the reading app's canonical open_id. When the backend
populates a mention_key on each at_users entry, it signals that the API-level mentions[]
array carries a more authoritative open_id and display name for the reading context. This PR adds
support for this two-level lookup: it threads the raw mentions[] array into the card converter,
indexes it by mention_key for O(1) access, and renders the canonical open_id + display name
whenever the link is resolvable. All existing fallback paths (no mention_key, nil mentions) are
preserved without behavioral change.
Change-Id: I00f846d76482adba315d07361c35909b71ca74c7
91-enjoy