allium check: field.unused doesn't count named-argument usage in Entity.created(...)

[abalmus-celonis]

Version: allium 3.5.0 (language versions: 1, 2, 3).

Bug: allium.field.unused flags an entity field as unused even when it's set via a named argument in an Entity.created(field: value, ...) constructor call in a rule's ensures: clause.

Repro (widget.allium):

-- allium: 3

entity Widget {
    name: String
}

rule MakeWidget {
    when: MakeWidget(name)
    ensures: Widget.created(name: name)
}

Actual:

Field 'Widget.name' is declared but not referenced elsewhere.

Expected: name is set by the Widget.created(name: name) call, so it shouldn't be flagged as unused. Usage tracking for this diagnostic appears to only look for member-access reads (entity.field), not named-argument writes in creation calls — which is the sole way most entity fields ever get populated in a typical spec (per the "Entity creation uses .created() exclusively" convention in the language reference).

Impact: this is the most disruptive of the three related reports (#58, #59) we filed — since .created() with named args is the canonical way to populate a new entity's fields, this diagnostic currently produces a false positive for nearly every field on every entity that's only ever created (not mutated) via a rule.