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).

server/__tests__/api.test.js

@@ -3120,3 +3120,39 @@ describe("GET /api/sessions/:id/outline", () => {
     assert.deepEqual(body.outputs, ["/w/src/b.ts", "/w/src/a.ts"]);
   });
 });
+
+describe("GET /api/sessions/:id/image", () => {
+  it("serves only an image the session itself read", async () => {
+    const sid = "read-image-" + Date.now();
+    const dir = fs.mkdtempSync(path.join(os.tmpdir(), "ah-read-image-"));
+    const png = path.join(dir, "shot.png");
+    const other = path.join(dir, "other.png");
+    const txt = path.join(dir, "notes.txt");
+    fs.writeFileSync(png, "PNGBYTES");
+    fs.writeFileSync(other, "OTHER");
+    fs.writeFileSync(txt, "text");
+    const read = (file_path) =>
+      post("/api/hooks/event", {
+        hook_type: "PostToolUse",
+        data: { session_id: sid, tool_name: "Read", tool_input: { file_path }, tool_response: {} },
+      });
+    await post("/api/hooks/event", { hook_type: "SessionStart", data: { session_id: sid } });
+    await read(png);
+    await read(txt);
+    const url = (p) => `/api/sessions/${sid}/image?path=${encodeURIComponent(p)}`;
+
+    const ok = await fetch(url(png));
+    assert.equal(ok.status, 200);
+    assert.equal(ok.headers["content-type"], "image/png");
+    assert.equal(ok.headers["x-content-type-options"], "nosniff");
+    assert.match(ok.headers["content-security-policy"], /sandbox/);
+    assert.equal(ok.body, "PNGBYTES");
+
+    // Never read by this session, not an image, not a session.
+    assert.equal((await fetch(url(other))).status, 404);
+    assert.equal((await fetch(url(txt))).status, 400);
+    assert.equal((await fetch(`/api/sessions/nope-image/image?path=${png}`)).status, 404);
+    fs.rmSync(dir, { recursive: true, force: true });
+    assert.equal((await fetch(url(png))).status, 404);
+  });
+});