#1189 A T3 checkout update shows in the sidebar's update pill, like the desktop and harness updates

[polymaniadeveloper-hub]

Task pingdotgg#1189, run run-f8807ae82d. Approved by T for commit f9891a9, which passed its checks and the QA gate.

What was asked

apps/web/src/components/sidebar/SidebarUpdatePill.tsx and SidebarChrome.tsx, apps/web/src/components/CheckoutUpdateNotification.tsx and CheckoutUpdate.logic.ts. A T3 run from a git checkout under the checkout supervisor offers its update (Update and restart, progress, undone) as a toast (CheckoutUpdateNotification), while the v2 sidebar, now the default, shows desktop updates in SidebarUpdatePill and harness updates in SidebarProviderUpdatePill. Show the checkout update in the sidebar's update area the same way: when the server is checkout-supervised and a newer commit is available, the update pill offers it with its subject and how many commits, Update and restart starts it, the pill shows installing, building and restarting, and how it ended (updated, or undone and why). Keep the toast only where the sidebar is not shown, or drop it, and say which. Keep the logic in CheckoutUpdate.logic.ts and its tests.

Done when

1. In a browser with the v2 sidebar, connected to a checkout-supervised server that has a newer commit, the sidebar's update area shows a checkout update pill with the new commit's subject (or short hash) and the commit count
2. With the v2 sidebar showing, no checkout update toast appears for the same update
3. Pressing Update and restart in the pill starts the checkout update, and while the update is starting the button cannot be pressed again
4. While the update runs, the pill shows installing, then building, then restarting, matching the server's phase
5. When the update is undone, the pill shows 'T3 update undone' with the reason; when it fails without being undone, the pill shows 'T3 could not update' with the reason
6. After a successful update, the tab that started it reloads by itself, and any other open tab's pill offers Reload with the new commit
7. If the update cannot be started (the request fails), the person is told it did not start and can try again
8. Dismissing an offered update in the pill hides it until a newer commit is available, using the same remembered dismissal as the toast
9. With the legacy sidebar setting on, the checkout update still appears as today's toast, with the same actions
10. A server that does not report the checkoutUpdate capability shows no checkout pill and no checkout toast
11. In the desktop app, the desktop update pill (check, download, install, and the Intel build warning) behaves exactly as before, and no checkout pill appears for its bundled server
12. Settings > Connections still shows the checkout version row with Update and restart / Check now
13. The pill's states are worked out in CheckoutUpdate.logic.ts, and CheckoutUpdate.logic.test.ts covers available, dismissed, each progress phase, undone, failed, reload and no-update
14. The result says that web was changed, that desktop was checked to be unchanged, and that mobile was not changed because it has no checkout update screen; it also names the T3 sidebar update pill as the piece reused and says what was not checked in a browser

Opened by the delivery engine after a person's approval. Merging is a separate step.