refactor(app): introduce attachment storage layer and draft lifecycle management

Replace inline data-URL image handling with a persistent attachment storage service, add draft lifecycle states (active/abandoned/sent) with generation tracking, and update fetchAgent to return project placement alongside agent snapshots.

packages/app/src/utils/image-attachments-from-files.test.ts

@@ -1,8 +1,10 @@
-import { describe, expect, it } from "vitest";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
 import {
   collectImageFilesFromClipboardData,
   filesToImageAttachments,
 } from "./image-attachments-from-files";
+import { __setAttachmentStoreForTests } from "@/attachments/store";
+import type { AttachmentStore } from "@/attachments/types";
 
 function createClipboardItem(params: {
   kind: string;
@@ -16,6 +18,52 @@ function createClipboardItem(params: {
   };
 }
 
+function createTestStore(): AttachmentStore {
+  let sequence = 0;
+  return {
+    storageType: "web-indexeddb",
+    async save(input) {
+      sequence += 1;
+      const id = input.id ?? `att-${sequence}`;
+      const mimeType = input.mimeType ?? "image/jpeg";
+      const fileName = input.fileName ?? null;
+      let byteSize = 0;
+      if (input.source.kind === "blob") {
+        byteSize = input.source.blob.size;
+      } else if (input.source.kind === "data_url") {
+        byteSize = input.source.dataUrl.length;
+      } else {
+        byteSize = input.source.uri.length;
+      }
+      return {
+        id,
+        mimeType,
+        storageType: "web-indexeddb",
+        storageKey: id,
+        fileName,
+        byteSize,
+        createdAt: 1700000000000 + sequence,
+      };
+    },
+    async encodeBase64() {
+      throw new Error("not used in this test");
+    },
+    async resolvePreviewUrl() {
+      throw new Error("not used in this test");
+    },
+    async delete() {},
+    async garbageCollect() {},
+  };
+}
+
+beforeEach(() => {
+  __setAttachmentStoreForTests(createTestStore());
+});
+
+afterEach(() => {
+  __setAttachmentStoreForTests(null);
+});
+
 describe("collectImageFilesFromClipboardData", () => {
   it("returns only image files from clipboard items", () => {
     const imagePng = new File([new Uint8Array([0, 1, 2, 3])], "paste.png", {
@@ -55,7 +103,7 @@ describe("collectImageFilesFromClipboardData", () => {
 });
 
 describe("filesToImageAttachments", () => {
-  it("converts files into data URI image attachments and keeps order", async () => {
+  it("persists files as attachment metadata in order", async () => {
     const pngFile = new File([new Uint8Array([0, 1, 2, 3])], "first.png", {
       type: "image/png",
     });
@@ -67,13 +115,34 @@ describe("filesToImageAttachments", () => {
 
     expect(attachments).toEqual([
       {
-        uri: "data:image/png;base64,AAECAw==",
+        id: "att-1",
         mimeType: "image/png",
+        storageType: "web-indexeddb",
+        storageKey: "att-1",
+        fileName: "first.png",
+        byteSize: 4,
+        createdAt: 1700000000001,
       },
       {
-        uri: "data:image/jpeg;base64,BAUGBw==",
+        id: "att-2",
         mimeType: "image/jpeg",
+        storageType: "web-indexeddb",
+        storageKey: "att-2",
+        fileName: "second",
+        byteSize: 4,
+        createdAt: 1700000000002,
       },
     ]);
   });
+
+  it("handles large files without creating data URLs", async () => {
+    const large = new File([new Uint8Array(4 * 1024 * 1024)], "large.png", {
+      type: "image/png",
+    });
+
+    const [attachment] = await filesToImageAttachments([large]);
+
+    expect(attachment?.storageType).toBe("web-indexeddb");
+    expect(attachment?.byteSize).toBe(4 * 1024 * 1024);
+  });
 });