* fix(desktop): stop retaining closed Settings views
Settings rotations left detached detail panes reachable from the web style registry's strong element sets. Backport the upstream weak cleanup design and cover the real Electron bundle with a forced-GC regression.\n\nKeep the established sibling-route topology; compact Back relies on route-name identity.
* test(app): synchronize Mermaid completion layout assertion
The streaming acceptance test can observe the intentional completion remount between visibility and layout sampling. Consult the existing completion promise around that measurement so the transition is not reported as diagram loss.
* test(app): isolate worktree restart from provider startup
