Content: pretty-printed JSON of template.data. Source: raw file bytes.
Document: the stored data (a script kind's source text, else
pretty-printed JSON).
Editor language hint: 'json' | 'typescript' | 'yaml' | 'plaintext'.
OptionaltemplateContent-only: the template's backing class + hydrator, echoed back so write can round-trip them unchanged. Absent for source.
Result of read — the editable body of one leaf.