MAESTRO: extract headers from dropped EML

frontend/src/__tests__/FileDropZone.test.tsx

@@ -97,7 +97,9 @@ describe("FileDropZone", () => {
 
   it("reads dropped EML/TXT file content", () => {
     const handleContent = vi.fn();
-    const restore = mockFileReader("Header from file");
+    const restore = mockFileReader(
+      "From: sender@example.com\r\nSubject: Hello\r\n\r\nBody: should be ignored",
+    );
     const { container } = render(<FileDropZone onFileContent={handleContent} />);
     const dropZone = getDropZone(container);
     const file = new File(["Header from file"], "sample.eml", { type: "message/rfc822" });
@@ -108,7 +110,7 @@ describe("FileDropZone", () => {
 
     restore();
 
-    expect(handleContent).toHaveBeenCalledWith("Header from file");
+    expect(handleContent).toHaveBeenCalledWith("From: sender@example.com\nSubject: Hello");
   });
 
   it("rejects unsupported file types with feedback", () => {

frontend/src/components/FileDropZone.tsx

@@ -58,6 +58,28 @@ const getFirstFile = (transfer: DataTransfer | null): File | null => {
   return null;
 };
 
+const normalizeLineEndings = (value: string): string =>
+  value.replace(/\r\n/g, "\n").replace(/\r/g, "\n");
+
+const extractHeaderBlock = (content: string): string => {
+  const normalized = normalizeLineEndings(content);
+  const lines = normalized.split("\n");
+  const headerLines: string[] = [];
+
+  for (const line of lines) {
+    if (line.trim() === "") {
+      break;
+    }
+    headerLines.push(line);
+  }
+
+  if (headerLines.length === 0) {
+    return normalized.trim();
+  }
+
+  return headerLines.join("\n").trimEnd();
+};
+
 export default function FileDropZone({ onFileContent }: FileDropZoneProps) {
   const [isDragging, setIsDragging] = useState(false);
   const [error, setError] = useState<string | null>(null);
@@ -80,7 +102,7 @@ export default function FileDropZone({ onFileContent }: FileDropZoneProps) {
     reader.onload = () => {
       const result = reader.result;
       const content = typeof result === "string" ? result : "";
-      onFileContent(content);
+      onFileContent(extractHeaderBlock(content));
     };
     reader.onerror = () => {
       setError("Unable to read the dropped file.");