Add project Export button to Easy Gen

Easy Gen's "Save" persists into FunPack's own project store on that
machine, same as the Editor's autosave — it was never a way to move a
project between machines. The backend route for that (download the actual
.funpack_project.json, re-importable via "Load Project File...") already
existed and easy_gen/frontend/api.js already had the URL helper, but no
button anywhere called it, unlike the Editor's File > "Save Project File...".
Added an "Export..." button next to Save that flushes a save first, then
downloads the project file.

easy_gen/frontend/app.js

@@ -19,6 +19,7 @@
   const advancedBtn = document.getElementById("easy-advanced-btn");
   const projectsBtn = document.getElementById("easy-projects-btn");
   const saveBtn = document.getElementById("easy-save-btn");
+  const exportBtn = document.getElementById("easy-export-btn");
 
   const preview = window.EasyPreview.create(document.getElementById("easy-preview"));
 
@@ -52,6 +53,7 @@
     uploadBtn.disabled = !p;
     galleryBtn.disabled = !p;
     saveBtn.disabled = !p;
+    exportBtn.disabled = !p;
     if (p && !promptFocused) {
       const text = p.global_prompt || "";
       if (promptEl.value !== text) promptEl.value = text;
@@ -142,6 +144,20 @@
   projectsBtn.onclick = () => window.ProjectMenu.open({ dismissable: !!S.get().project });
   galleryBtn.onclick = () => window.EasyGallery.open();
 
+  // "Save" persists into FunPack's own project store on THIS machine — the same mechanism
+  // as the Editor's autosave. It doesn't help moving a project off a rental GPU box. This
+  // downloads the actual .funpack_project.json file (re-importable via "Load Project
+  // File…" on another machine), same as the Editor's File ▸ "Save Project File…".
+  exportBtn.onclick = async () => {
+    const st = S.get();
+    if (!st.project) return;
+    try { await S.save(); } catch (_) { /* export the last-saved version anyway */ }
+    const a = document.createElement("a");
+    a.href = API.downloadProjectUrl(st.project.id);
+    a.download = "";
+    document.body.appendChild(a); a.click(); document.body.removeChild(a);
+  };
+
   let saveResetTimer = null;
   saveBtn.onclick = async () => {
     if (saveResetTimer) clearTimeout(saveResetTimer);

easy_gen/frontend/index.html

@@ -56,6 +56,8 @@
       <span class="health-chip" id="easy-health-chip"></span>
       <div class="menubar-right">
         <button class="btn ghost tiny" id="easy-save-btn" type="button">Save</button>
+        <button class="btn ghost tiny" id="easy-export-btn" type="button"
+          title="Download this project as a .funpack_project.json file — e.g. to move it off a rental machine">Export…</button>
         <button class="btn ghost tiny" id="easy-projects-btn" type="button">Projects…</button>
       </div>
     </header>