make some overall QoL improvements

public/js/attachments.js

@@ -27,6 +27,7 @@ export function createAttachmentComposer({onChange, onError}) {
     const preview = document.getElementById("uploadPreviews");
     const composer = document.querySelector(".input-container");
     let items = [];
+    const drafts = new Map();
     let busy = false;
     let limits = {maxSizeMb: 10, maxFiles: 5};
     fetch("/uploads/config").then(r => r.ok ? r.json() : limits).then(value => { limits = value; }).catch(() => {});
@@ -73,13 +74,13 @@ export function createAttachmentComposer({onChange, onError}) {
             const result = await response.json();
             if (!response.ok) throw new Error(result.error || "Upload failed");
             item.metadata = result;
-            if (!items.includes(item)) void fetch(`/attachments/${result.id}`, {method: "DELETE"});
+            if (![items, ...drafts.values()].some(draft => draft.includes(item))) void fetch(`/attachments/${result.id}`, {method: "DELETE"});
         } catch (error) {
             if (error.name !== "AbortError") item.error = error.message || "Upload failed";
         }
         item.uploading = false;
         item.controller = null;
-        render();
+        if (items.includes(item)) render();
     };
     const add = files => {
         if (busy) return;
@@ -117,6 +118,25 @@ export function createAttachmentComposer({onChange, onError}) {
             }
             items = [];
             render();
+        },
+        saveDraft(chatId) {
+            if (chatId != null) drafts.set(chatId, items);
+            items = [];
+            render();
+        },
+        restoreDraft(chatId) {
+            items = drafts.get(chatId) || [];
+            drafts.delete(chatId);
+            render();
+        },
+        discardDraft(chatId) {
+            const saved = drafts.get(chatId) || [];
+            drafts.delete(chatId);
+            for (const item of saved) {
+                item.controller?.abort();
+                URL.revokeObjectURL(item.preview);
+                if (item.metadata) void fetch(`/attachments/${item.metadata.id}`, {method: "DELETE"});
+            }
         }
     };
 }