feat(resume): Resume in the kebab menu (A1) + harden the resume kickoff (A2)

A1 — SessionMenu gains a Resume item, gated to status!=="finalized" && !archived
(matching the backend's 409 read-only guard), wired in AppShell to doResume ->
POST /sessions/:id/resume. SessionMenu.test.tsx (3 tests); frontend 96/96, tsc clean.

A2 — diagnosis-first clean-room repro driving `pi --mode rpc` with the backend's
exact resume handshake shows the cold-start stall NO LONGER reproduces on pi
0.79.4 (8/8 chained into `tht session show` + `read SKILL.md` in-turn, fresh and
partway sessions). The earlier narrate-and-stop predates the pi upgrade.
Defense-in-depth anyway: RIPRENDI_KICKOFF hardened to force the in-turn tool call
(gate_resume_kickoff.test.js + live regression 2/2). Gate JS 34/34.

PROJECT_STATE open-item #1 (resume stall) flipped to RESOLVED; cross-model resume
robustness folded into workstream G.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/shell/AppShell.tsx

@@ -118,6 +118,7 @@ export function AppShell() {
       <SessionMenu
         session={s}
         groups={groups}
+        onResume={() => doResume(s.id)}
         onView={() => setPanelSession(s)}
         onRename={() => setRenameTarget(s)}
         onMove={(g) => move(s, g)}

frontend/src/shell/SessionMenu.test.tsx

@@ -0,0 +1,49 @@
+import { render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { vi } from "vitest";
+import { SessionMenu } from "./SessionMenu";
+import type { SessionSummary } from "../api/types";
+
+const base: SessionSummary = {
+  id: "s1", status: "open", question: "q", summary: null,
+  created_at: "2026-01-01T00:00:00Z", updated_at: null, author: null,
+  name: null, group: null, archived: false,
+};
+
+function renderMenu(over: Partial<SessionSummary>, onResume = vi.fn()) {
+  render(
+    <SessionMenu
+      session={{ ...base, ...over }}
+      groups={[]}
+      onResume={onResume}
+      onView={vi.fn()}
+      onRename={vi.fn()}
+      onMove={vi.fn()}
+      onNewGroup={vi.fn()}
+      onArchiveToggle={vi.fn()}
+      onDelete={vi.fn()}
+    />,
+  );
+  return onResume;
+}
+
+test("Resume shows for an open, non-archived session and calls onResume", async () => {
+  const onResume = renderMenu({ status: "open", archived: false });
+  await userEvent.click(screen.getByRole("button", { name: /session actions/i }));
+  await userEvent.click(await screen.findByText("Resume"));
+  expect(onResume).toHaveBeenCalledTimes(1);
+});
+
+test("Resume is hidden for a finalized session", async () => {
+  renderMenu({ status: "finalized" });
+  await userEvent.click(screen.getByRole("button", { name: /session actions/i }));
+  await screen.findByText("Split view"); // menu is open
+  expect(screen.queryByText("Resume")).not.toBeInTheDocument();
+});
+
+test("Resume is hidden for an archived session", async () => {
+  renderMenu({ status: "open", archived: true });
+  await userEvent.click(screen.getByRole("button", { name: /session actions/i }));
+  await screen.findByText("Split view"); // menu is open
+  expect(screen.queryByText("Resume")).not.toBeInTheDocument();
+});

frontend/src/shell/SessionMenu.tsx

@@ -5,6 +5,7 @@ import type { SessionSummary } from "../api/types";
 interface Props {
   session: SessionSummary;
   groups: string[];
+  onResume: () => void;
   onView: () => void;
   onRename: () => void;
   onMove: (group: string) => void;
@@ -16,7 +17,10 @@ interface Props {
 const itemCls =
   "flex w-full cursor-default select-none items-center rounded-md px-2 py-1.5 text-sm outline-none data-highlighted:bg-accent data-highlighted:text-accent-foreground";
 
-export function SessionMenu({ session, groups, onView, onRename, onMove, onNewGroup, onArchiveToggle, onDelete }: Props) {
+export function SessionMenu({ session, groups, onResume, onView, onRename, onMove, onNewGroup, onArchiveToggle, onDelete }: Props) {
+  // Resume re-enters the workflow; only meaningful while the session is still live
+  // (the backend returns 409 for finalized/archived, matching this guard).
+  const canResume = session.status !== "finalized" && !session.archived;
   return (
     <Menu.Root>
       <Menu.Trigger
@@ -29,6 +33,9 @@ export function SessionMenu({ session, groups, onView, onRename, onMove, onNewGr
       <Menu.Portal>
         <Menu.Positioner side="bottom" align="end" sideOffset={4}>
           <Menu.Popup className="z-50 min-w-44 rounded-lg bg-popover p-1 text-popover-foreground shadow-md ring-1 ring-foreground/10 outline-none">
+            {canResume && (
+              <Menu.Item className={itemCls} onClick={onResume}>Resume</Menu.Item>
+            )}
             <Menu.Item className={itemCls} onClick={onView}>Split view</Menu.Item>
             <Menu.Item className={itemCls} onClick={onRename}>Rename</Menu.Item>
             <Menu.SubmenuRoot>