Add a QTI assessment-item type and renderable preset-bit ordering

[rtibbles]

Overview

Add the QTI assessment-item type and a stable preset→bit ordering for the renderable bitmask — both consumed by Studio and Kolibri.

Context

• AssessmentItem.type values come from le_utils.constants.exercises; Studio Adding raw deployments app to fle-utils #1 needs a QTI value.
• File.included_presets (studio Separated constants #8, kolibri Trying init file #10) is a bitmask whose bit positions derive from a stable preset ordering — like Kolibri's metadata-label bitmasks, which take each label's bit from its index in the le-utils ordered list.

The Change

• Add a QTI assessment-item type to constants.exercises.
• Define the preset→bit ordering for the renderable bitmask as append-only: existing presets keep their bit; new presets get the next.

Acceptance Criteria

• constants.exercises exposes a QTI assessment-item type
• A stable, append-only preset→bit mapping backs the renderable bitmask
• Studio and Kolibri can both import the type and the bit mapping

References

• studio Adding raw deployments app to fle-utils #1, studio Separated constants #8, kolibri Trying init file #10

AI usage

Architecture decided with the maintainer across an iterative session: blanket QTI type with the item XML in raw_data; XSD-authoritative validation across all sources; a legacy→QTI global migration with an API-layer dual-read; ricecooker upload delegating to the AssessmentItem serializer; and a Perseus custom-interaction contract confirmed against the QTI 3.0 specification. Claude mapped the existing publish/validation/ricecooker code, proposed the breakdown, and drafted each issue; the maintainer steered every decision and reviewed throughout.