test(deploy): preserve empty Foundry map filters

infra/deploy-runner/build-module-foundry-filter-toggle-artifact.mjs

@@ -64,8 +64,8 @@ async function assertFilterToggleBoundary() {
   const helper = await readFile(resolve(foundryRoot, files[1]), "utf8");
   for (const marker of [
     "toggleMapPresentationFacetSelection",
-    "const { [field]: _removed, ...unconstrained } = facets",
-    "return unconstrained",
+    "const { [field]: _removed, ...remaining } = facets",
+    "return { [field]: [] }",
   ]) {
     if (!helper.includes(marker)) throw new Error(`foundry_filter_toggle_helper_missing:${marker}`);
   }
@@ -77,7 +77,9 @@ async function assertFilterToggleBoundary() {
 
   const test = await readFile(resolve(foundryRoot, files[2]), "utf8");
   for (const marker of [
-    "interactive deselect of the last chip removes the facet constraint",
+    "interactive deselect of the last chip preserves the zero-match state",
+    "the first chip selected after a saved empty view removes every empty sentinel",
+    "a complete interactive toggle cycle returns to zero matches instead of all",
     "interactive deselect preserves other values and facet constraints",
     "deselecting the last chip remains empty and never normalizes to all",
   ]) {

infra/deploy-runner/test_module_foundry_filter_toggle_artifact.py

@@ -75,9 +75,10 @@ class ModuleFoundryFilterToggleArtifactTest(unittest.TestCase):
             preview = (payload / EXPECTED_FILES[0]).read_text(encoding="utf-8")
             regression = (payload / EXPECTED_FILES[2]).read_text(encoding="utf-8")
             self.assertIn("toggleMapPresentationFacetSelection", helper)
-            self.assertIn("return unconstrained", helper)
+            self.assertIn("return { [field]: [] }", helper)
             self.assertIn("filters: toggleMapPresentationFacetSelection(filters, field, value)", preview)
-            self.assertIn("interactive deselect of the last chip removes the facet constraint", regression)
+            self.assertIn("interactive deselect of the last chip preserves the zero-match state", regression)
+            self.assertIn("a complete interactive toggle cycle returns to zero matches instead of all", regression)
 
             with tarfile.open(first_artifact, "r:gz") as archive:
                 members = archive.getmembers()