feat: session persistence

ts/src/browser.ts

@@ -112,10 +112,38 @@ function showConfirm(
   });
 }
 
+// --- Persistence -------------------------------------------------------------
+const STORAGE_KEY = "monodisplay_autosave";
+
+function saveToStorage() {
+  try {
+    const buf = file.toBuffer();
+    const b64 = btoa(String.fromCharCode(...buf));
+    localStorage.setItem(STORAGE_KEY, JSON.stringify({ filename: currentFilename, data: b64 }));
+  } catch {}
+}
+
+function loadFromStorage() {
+  try {
+    const raw = localStorage.getItem(STORAGE_KEY);
+    if (!raw) return;
+    const { filename, data } = JSON.parse(raw);
+    const bytes = Uint8Array.from(atob(data), c => c.charCodeAt(0));
+    const parsed = new MonoDisplay.MonoDisplayParser().parse(bytes.buffer);
+    file = new MonoDisplayFile(parsed.sections);
+    currentFilename = filename;
+    const filenameEl = document.getElementById("filename");
+    if (filenameEl) filenameEl.textContent = filename;
+    isDirty = true;
+    document.getElementById("filename")?.classList.add("dirty");
+  } catch {}
+}
+
 // --- Dirty tracking ----------------------------------------------------------
 function markDirty() {
   isDirty = true;
   document.getElementById("filename")?.classList.add("dirty");
+  saveToStorage();
 }
 function markClean() {
   isDirty = false;
@@ -797,4 +825,5 @@ window.addEventListener("beforeunload", (e) => {
   if (isDirty) e.preventDefault();
 });
 
+loadFromStorage();
 triggerPreview();