- pact.AdminActionExtension.Form with AdminFormExtension: a fields
document (fields.yaml format plus before:/after:/zone: and a tabs:
list) given as an AdminFS path or YAML bytes, Load and Save hooks,
AdminFormLoad/Save/SaveResult, AdminFormErrors and zone constants
- cabana compileFormExtensions places extension fields at owner
anchors at boot, regrouping an extended form by tab
- save lifts extension values before any owner path and runs Save in
the record's transaction after the owner row; show merges Load
- TestFormExtensionTracer: c after a on a, b gives a, c, b through the
admin API, stored in the contributor's table
