Fork assistant turns into new drafts (#1788)

* feat(chat): fork assistant turns into new drafts

Builds chat-history attachments on the daemon and routes them into draft composers so users can continue an assistant turn in an existing workspace tab or New Workspace.

* fix(chat): clean up fork draft handling

* fix(chat): address fork draft review feedback

* fix(server): build fork context from bounded timeline

* fix(app): restore assistant turn footer in streams

* fix(app): preserve fork draft setup

* fix(app): tighten assistant fork footers

* fix(app): lock active fork draft handoff

* fix(app): preserve attachment-only draft retries

* fix(app): unify composer attachment scopes

* fix(app): align chat history attachment labels

* fix(app): centralize attachment pill content

* fix(app): trim fork context for workspace naming

packages/app/src/composer/attachments/workspace.test.ts

@@ -0,0 +1,72 @@
+import { describe, expect, it } from "vitest";
+import type { WorkspaceComposerAttachment } from "@/attachments/types";
+import {
+  buildDraftWorkspaceAttachmentScopeKey,
+  resetWorkspaceAttachmentsStore,
+  useWorkspaceAttachmentsStore,
+} from "@/attachments/workspace-attachments-store";
+import { removeSentContextAttachments } from "./workspace-cleanup";
+
+function chatHistoryAttachment(): WorkspaceComposerAttachment {
+  return {
+    kind: "chat_history",
+    id: "chat_history:draft-1",
+    attachment: {
+      type: "text",
+      mimeType: "text/plain",
+      contextKind: "chat_history",
+      title: "Chat history",
+      text: "Previous chat.",
+    },
+    source: {
+      serverId: "local",
+      agentId: "agent-1",
+    },
+  };
+}
+
+function pullRequestContextAttachment(): WorkspaceComposerAttachment {
+  return {
+    kind: "github.pull_request_comment",
+    id: "comment-1",
+    title: "Comment",
+    text: "Please check this.",
+  };
+}
+
+function browserElementAttachment(): WorkspaceComposerAttachment {
+  return {
+    kind: "browser_element",
+    attachment: {
+      url: "https://example.com",
+      selector: "button.primary",
+      tag: "button",
+      text: "Click me",
+      outerHTML: '<button class="primary">Click me</button>',
+      computedStyles: {},
+      boundingRect: { x: 0, y: 0, width: 100, height: 40 },
+      reactSource: null,
+      parentChain: [],
+      children: [],
+      formatted: "button.primary\nClick me",
+    },
+  };
+}
+
+describe("workspace composer attachment cleanup", () => {
+  it("clears sent scoped context attachments from their stores", () => {
+    resetWorkspaceAttachmentsStore();
+    const scopeKey = buildDraftWorkspaceAttachmentScopeKey("draft-1");
+    const chatHistory = chatHistoryAttachment();
+    const pullRequestContext = pullRequestContextAttachment();
+    const browserElement = browserElementAttachment();
+    useWorkspaceAttachmentsStore.getState().setWorkspaceAttachments({
+      scopeKey,
+      attachments: [chatHistory, pullRequestContext, browserElement],
+    });
+
+    removeSentContextAttachments([chatHistory, pullRequestContext, browserElement]);
+
+    expect(useWorkspaceAttachmentsStore.getState().attachmentsByScope[scopeKey]).toBeUndefined();
+  });
+});