Heptabase card cross-linking via CLI

The key finding

Markdown append does NOT create real cross-links in Heptabase. Wiki-link syntax like [[Card Title]] written through heptabase note create or heptabase note append is stored as literal text inside a text node — it renders in the card as the plain string [[Card Title]], not as a clickable link.

Real internal links are dedicated ProseMirror node types (not marks). The only way to create them via the CLI is heptabase note save (or journal save) with explicit ProseMirror JSON.

Two link schemas: pick the right one for your target

Heptabase uses different node types depending on whether you're linking to a card (note, pdf, highlight, etc.) or to a journal. Getting this wrong produces a pill that renders as "Invalid card" in the UI.

Linking to a card (note, pdf, highlight, etc.)

{ "type": "card", "attrs": { "cardId": "<target-card-uuid>" } }