feat(cloud): rename custom sandbox env images

[tatoalo]

Problem

Custom sandbox base images in cloud environments could be created and deleted but never renamed.

[trunk-io]

😎 Merged successfully - details.

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit 9e05615.}

[stamphog]

New feature touching API contracts and UI behavioral logic with zero reviews, authored outside any owning team — needs a human reviewer familiar with the sandbox custom images area before it can be auto-approved.

[greptile-apps]

Prompt To Fix All With AI

Fix the following 3 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 3
packages/ui/src/features/settings/sections/environments/CloudEnvironmentsSettings.tsx:480-481
**Failed Rename Rejects Unhandled**

When the PATCH fails because of a network, authentication, or backend error, `mutateAsync` rejects and both callers discard that promise with `void`. The mutation callback shows a toast but does not consume the rejection, so the application also emits an unhandled promise rejection.

```suggestion
    try {
      await updateImageMutation.mutateAsync({ id: renameImage.id, name });
      setRenameImage(null);
    } catch {
      // The mutation's onError callback displays the failure.
    }
```

### Issue 2 of 3
packages/ui/src/features/settings/sections/environments/CloudEnvironmentsSettings.tsx:1154-1159
**Enter Bypasses Pending Guard**

The Enter handler invokes the rename callback even while the first request is pending, unlike the loading Save button. Holding or quickly pressing Enter twice can therefore start concurrent PATCH requests and display duplicate mutation feedback.

```suggestion
                  onKeyDown={(e) => {
                    if (e.key === "Enter") {
                      e.preventDefault();
                      if (!updateImageMutation.isPending) {
                        void handleRenameImage();
                      }
                    }
                  }}
```

### Issue 3 of 3
packages/ui/src/features/settings/sections/environments/useSandboxCustomImages.ts:160
**Partial Response Replaces Detail Cache**

If the PATCH endpoint returns only the updated fields, as the new client test permits, this call replaces the complete detail-cache object with `{ id, name }`. An open build-log view can then lose fields such as status and build output because this path invalidates only the list cache, not the detail entry.

_{Reviews (1): Last reviewed commit: "feat(cloud): rename custom sandbox env i..." | Re-trigger Greptile}

[stamphog]

The code quality is solid and the bot-flagged P1/P2 issues were addressed, but the author is outside the owning team and this PR adds a new API contract method plus behavioral UI logic in the sandbox environments area, which requires a human reviewer familiar with that area before auto-approval.