fix(files): make dropped-file handling explicit

webui/scripts/test-file-drop-zone-structure.mjs

@@ -0,0 +1,41 @@
+import { readFileSync } from "node:fs";
+
+const source = readFileSync(new URL("../src/components/FileDropZone.tsx", import.meta.url), "utf8");
+const normalized = source.replace(/\s+/g, " ");
+
+function assertIncludes(fragment, message) {
+  if (!normalized.includes(fragment.replace(/\s+/g, " "))) throw new Error(message);
+}
+
+assertIncludes(
+  "function prepareFileDrag(event: ReactDragEvent<HTMLDivElement>) { event.preventDefault(); event.stopPropagation();",
+  "drag enter/over must prevent the browser default and stop propagation"
+);
+assertIncludes("onDragEnter={prepareFileDrag}", "drag enter must use the guarded file-drag handler");
+assertIncludes("onDragOver={prepareFileDrag}", "drag over must use the guarded file-drag handler");
+assertIncludes(
+  "onDragLeave={(event) => { event.preventDefault(); event.stopPropagation();",
+  "drag leave must prevent the browser default and stop propagation"
+);
+assertIncludes(
+  "onDrop={(event) => { event.preventDefault(); event.stopPropagation(); setDragActive(false);",
+  "drop must prevent the browser default and stop propagation before resolving files"
+);
+assertIncludes(
+  "if (interactionDisabled) { onRejectedDrop?.(\"disabled\"); return; }",
+  "disabled drops must route the disabled rejection reason"
+);
+assertIncludes(
+  "void resolveDroppedFiles(event.dataTransfer).then((files) => {",
+  "drop must route the event DataTransfer through the shared resolver"
+);
+assertIncludes(
+  "if (files.length === 0) { onRejectedDrop?.(\"empty\"); return; } void handleFiles(files);",
+  "resolved files and empty drops must be routed through their explicit callbacks"
+);
+assertIncludes(
+  ".catch(() => onRejectedDrop?.(\"unreadable\"))",
+  "resolver failures must route the unreadable rejection reason"
+);
+
+console.log("FileDropZone event and result routing structure is intact.");