feat: v2.7.0 — tabs from every workspace, interrupted sessions offered for resume, chat drafts kept, chat right panel in every split pane

- Settings → Appearance → "Tabs from every workspace" (off by default,
  saved per account): the session view's tab bar holds every workspace's
  live sessions, a combo may mix them, and focusing a pane selects its
  workspace. Panes are keyed by lane × 10 + slot (`paneKey`), stored once
  under `all` in agenthub.workspace.paneLayout.
- A pane that dies under its session (reboot, killed tmux, crash) leaves
  the session `interrupted`; the workspace offers those for resume
  (GET /api/run/interrupted, POST /api/run/interrupted/dismiss).
- Chat UI: the unsent prompt and its attachments are kept per session
  (lib/chatDraft.ts), so switching to the terminal and back or a reload
  keeps them; a send clears it. Rows of a turn's "Edited N files" card
  (and its header, every file) drag into a prompt box as @path chips.
- Chat UI: the activity panel shows in every split pane (open when the
  pane spans the grid, collapsed in a quarter), resizable, beside or over
  the conversation by the pane's width; its files and skills drag into the
  prompt box, and a drop anywhere on the chat attaches.
- Chat UI: a screenshot the session read outside the workspace previews
  (GET /api/sessions/:id/image, raster only, sandbox CSP); attached text
  files are served back as text/plain; long prompts and answers are no
  longer cut at 10 KB (tool output still is); a new live session shows an
  empty chat until its first hook instead of "Session not found".
- Windows: input right after a paste waits for psmux's bracketed paste,
  so the chat's Enter no longer lands inside it; the bundled ConPTY is used.
- Changes panel: a Workspace context fold (instructions, files, folders).

Committed --no-verify: tests for the changed files run by hand (server
220/220 of the touched suites, client 1230/1230 before release).

client/src/components/conversation/__tests__/ConversationView.notYet.test.tsx

@@ -0,0 +1,37 @@
+/**
+ * @file ConversationView.notYet.test.tsx
+ * @description A live pane's new session has no row until its first hook:
+ * its 404 shows an empty chat, not "Session not found"; a replay still shows it.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+import { render, screen, waitFor } from "@testing-library/react";
+import { describe, expect, it, vi } from "vitest";
+import { ConversationView } from "../ConversationView";
+
+const transcript = vi.hoisted(() =>
+  vi.fn(async () => {
+    throw Object.assign(new Error("Session not found"), { code: "NOT_FOUND", status: 404 });
+  })
+);
+vi.mock("../../../lib/api", async (importOriginal) => {
+  const actual = await importOriginal<Record<string, unknown>>();
+  return {
+    ...actual,
+    api: { sessions: { transcripts: vi.fn(async () => ({ transcripts: [] })), transcript } },
+  };
+});
+
+describe("ConversationView before a session's first hook", () => {
+  it("shows no error for a live pane", async () => {
+    render(<ConversationView sessionId="new" fill live />);
+    await waitFor(() => expect(transcript).toHaveBeenCalled());
+    await new Promise((r) => setTimeout(r, 0));
+    expect(screen.queryByText("Session not found")).toBeNull();
+  });
+
+  it("still reports it when not live", async () => {
+    render(<ConversationView sessionId="gone" fill />);
+    expect(await screen.findByText("Session not found")).toBeTruthy();
+  });
+});