The gate's widget-descriptor CONSTRUCTION, extracted into pure testable functions.
Each builder turns plain params into a ui_request descriptor (spec §4.1 taxonomy):
buildSelectRequest, buildMultiselectRequest, buildArtifactGate, buildInfoRequest,
buildFreetextRequest, withChildLinkage. No Pi context, no I/O -- the part of the
gate fully testable in L1 (in JS, in-language, no Python mirror).
Validation in the builders (not just happy-path): select requires title + array
options; multiselect allow_empty:false with zero options throws (a broken widget);
artifact-gate requires an artifact with a kind + a valid action.kind
(confirm/approve_reject/view_only); info level must be info/warning/error. The
Altro escape hatch with freetext linkage is always injected on blocking pick
widgets (no-limbo invariant).
L1: 14 node:test cases -- 3 golden files (select_F1, multiselect_F4,
artifact_gate_F5) pin the exact descriptor shape; fuzzy tests assert bad params
throw clearly rather than silently producing a broken widget.
package.json wires 'npm test' -> node --test (runs alongside pytest). The gate
GLUE (emission, anti-bypass, no-limbo loop) is C2, verified at L2.
