feat(javascript): report observed export property presence (#1160)

* feat(javascript): report observed export property presence

Extend compare_javascript_export_shapes so each retained return variant
lists observed property names and each change reports presence independently
of value resolution. Complete parent coverage classifies one-sided names as
added or removed even when static values stay unknown.

Fixes #725

* test(javascript): match unknown export-shape values by availability

Nested availability objects include a reason when values stay unresolved.
Assert availability through objectContaining so presence-only added and
removed rows still verify unknown values.

* fix(javascript): preserve uncertain export property presence and locations

* fix(javascript): normalize presence and preserve local property coverage

* fix(javascript): require present discriminants for return pairing

* fix(javascript): normalize retained shapes before comparison

* refactor(javascript): share return projection with executable examples

* fix(javascript): localize uncertainty for missing mutated slots

* fix(javascript): bind advertised export examples to exact artifacts

* fix(javascript): keep uncertain property flow as candidates

---------

Co-authored-by: morluto <76467478+morluto@users.noreply.github.com>

src/domain/javascript/javascriptExportShapeSelection.ts

@@ -10,6 +10,9 @@ import {
 import { compareCodePoints } from "../canonicalOrdering.js";
 
 type Shape = ProjectedExportReturnShapes["static_return_shapes"][number];
+type Field = Shape["fields"][number];
+type NormalizedField = Field & { presence: NonNullable<Field["presence"]> };
+type NormalizedShape = Omit<Shape, "fields"> & { fields: NormalizedField[] };
 type SelectorResult = JavaScriptExportShapeComparisonResult["left"];
 type SelectorBase = Omit<SelectorResult, "status" | "selected_node_id">;
 type ReturnShapeSelection =
@@ -55,7 +58,7 @@ export type SelectedJavaScriptExport =
 
 /** Complete return-shape inventory retained from an authenticated projection. */
 export interface RetainedJavaScriptExportShapes {
-  readonly shapes: readonly Shape[];
+  readonly shapes: readonly NormalizedShape[];
   readonly omitted: number;
 }
 
@@ -126,11 +129,22 @@ export const selectJavaScriptExport = (
   };
 };
 
-/** Retain every projected return variant. */
+/** Retain every variant and normalize legacy presence on comparison-owned copies. */
 export const retainJavaScriptExportShapes = (
   selection: SelectedJavaScriptExport,
 ): RetainedJavaScriptExportShapes => {
-  const shapes = selection.projection?.static_return_shapes ?? [];
+  const shapes = (
+    selection.projection?.static_return_shapes ?? []
+  ).map<NormalizedShape>((shape) => ({
+    ...shape,
+    fields: shape.fields.map<NormalizedField>((field) => ({
+      ...field,
+      // Legacy unknown fields did not distinguish values from uncertain slots.
+      presence:
+        field.presence ??
+        (field.state === "unknown" ? "unknown-coverage" : "present"),
+    })),
+  }));
   return { shapes, omitted: 0 };
 };