fix(desktop): context option reloads discard unsaved edits #1651

Opening Desktop context settings can start a duplicate options request. If it completes after an edit, the response replaces the draft, clears dirty state and removes Save. A context-list refresh that replaces the same named context object can cause the same edit loss. Switching to another context whose load fails can also leave the prior context values visible.

Controlled component tests reproduced both edit-loss cases and the failed-context boundary before the repair. The macOS Desktop CI job in PR #1609 also saw Save detach, but no retained trace establishes that run's exact request ordering.

Expected behavior: load on intentional open or actual context-name change; same-name refreshes preserve the draft; stale responses after close or context changes cannot overwrite options or finish a newer load. Load failures show an error while retaining defaults; stale failures remain silent. Failed saves retain edits and retry behavior.

Repair and regression coverage are in PR #1609. It is included there because the defect blocked that PR's unchanged macOS Desktop E2E gate. The original Contexts E2E assertions and deadlines remain unchanged. Nine focused tests, 1,098 Desktop tests and nine targeted Electron E2E cases pass locally.

This issue tracks the separate context-settings product behavior; #1471 tracks workspace ID validation and detached-task recovery.