feat(installer): offer CodeGraph Pro beta signup after install and upgrade (#1297)

One-time, strictly opt-in prompt at the end of codegraph install and
codegraph upgrade to join the CodeGraph Pro beta waitlist (same list as
the getcodegraph.com homepage form). Nothing is sent unless the user
answers yes AND enters an email; either answer is recorded machine-wide
so no later install or upgrade re-asks, and --yes / non-interactive / CI
runs never see the prompt.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

__tests__/upgrade.test.ts

@@ -410,6 +410,69 @@ describe('runUpgrade', () => {
   });
 });
 
+// ---------------------------------------------------------------------------
+// Beta signup offer — fires ONLY after a real, successful binary update.
+// (The hook itself gates on TTY + the once-per-machine stored choice; see
+// __tests__/beta-signup.test.ts. Here we pin WHEN the upgrade path invokes it.)
+// ---------------------------------------------------------------------------
+
+describe('runUpgrade beta signup offer', () => {
+  function withSpy(deps: UpgradeDeps): { deps: UpgradeDeps; offered: () => number } {
+    let n = 0;
+    deps.offerBetaSignup = async () => { n += 1; };
+    return { deps, offered: () => n };
+  }
+
+  it('offers after a successful npm upgrade', async () => {
+    const { deps } = makeDeps({ method: { kind: 'npm', scope: 'global' }, currentVersion: '0.9.8' });
+    const { offered } = withSpy(deps);
+    expect(await runUpgrade({}, deps)).toBe(0);
+    expect(offered()).toBe(1);
+  });
+
+  it('does not offer on --check', async () => {
+    const { deps } = makeDeps({ method: { kind: 'npm', scope: 'global' }, currentVersion: '0.9.8' });
+    const { offered } = withSpy(deps);
+    expect(await runUpgrade({ check: true }, deps)).toBe(0);
+    expect(offered()).toBe(0);
+  });
+
+  it('does not offer when already up to date', async () => {
+    const { deps } = makeDeps({ method: { kind: 'npm', scope: 'global' }, currentVersion: '0.9.9' });
+    const { offered } = withSpy(deps);
+    expect(await runUpgrade({}, deps)).toBe(0);
+    expect(offered()).toBe(0);
+  });
+
+  it('does not offer when the upgrade fails', async () => {
+    const { deps } = makeDeps(
+      { method: { kind: 'npm', scope: 'global' }, currentVersion: '0.9.8' },
+      1 // npm exits non-zero
+    );
+    const { offered } = withSpy(deps);
+    expect(await runUpgrade({}, deps)).toBe(1);
+    expect(offered()).toBe(0);
+  });
+
+  it('does not offer on npx / source no-op paths', async () => {
+    for (const method of [
+      { kind: 'npx' } as const,
+      { kind: 'source', root: '/dev/codegraph' } as const,
+    ]) {
+      const { deps } = makeDeps({ method, currentVersion: '0.9.8' });
+      const { offered } = withSpy(deps);
+      expect(await runUpgrade({}, deps)).toBe(0);
+      expect(offered()).toBe(0);
+    }
+  });
+
+  it('a throwing offer never fails the upgrade', async () => {
+    const { deps } = makeDeps({ method: { kind: 'npm', scope: 'global' }, currentVersion: '0.9.8' });
+    deps.offerBetaSignup = async () => { throw new Error('boom'); };
+    expect(await runUpgrade({}, deps)).toBe(0);
+  });
+});
+
 // ---------------------------------------------------------------------------
 // Post-upgrade self-heal of installed agent surfaces
 // ---------------------------------------------------------------------------