Referenced TRANSACTIONAL subinterface renders without its transaction bar

[stefjoosten]

What happens now

When an interface reference (<expr> INTERFACE Foo) targets a TRANSACTIONAL interface Foo, the referenced subinterface renders without its transaction bar (SAVE/CANCEL) and without buffering — its fields render inline and autosave, as if the interface were not transactional.

Empirically (v2.4.6 / Ampersand v5.9.2):

Foo rendered as	own <app-foo> component	transaction bar
top-level (route / embed)	yes	yes
<expr> INTERFACE Foo (subinterface reference)	no	no

Cause

A reference is compiled by inlining the referenced interface's box into the parent component's template (<app-box-form propertyName="foo" [data]="[resource.foo]">) instead of instantiating Foo's own component. The transaction bar is mounted in ampersand-interface.class.ts → setResource() → mountTransactionBar() when resolveMode()==='Transactional', and that only runs inside an instantiated interface component. An inlined referenced box never reaches it.

Note: @HostBinding('class.ampersand-transactional-interface') already carries the comment "required by the TRANSACTIONAL feature (also for subinterfaces)" — the intent for transactional subinterfaces exists; the mount path just isn't reached for references.

Desired

A referenced TRANSACTIONAL subinterface gets its transaction bar (its own buffer + SAVE), just like when rendered top-level.

Minimal repro

A non-transactional wrapper that references a TRANSACTIONAL interface as a subinterface:

INTERFACE Wrapper : I[SESSION] cRud BOX<FORM>
  [ "x" : <expr> INTERFACE Login ]   -- Login is a TRANSACTIONAL INTERFACE

Done when the login commits via a transaction bar rendered at the subinterface.