Add basic PRK.Client options window toggled with F12

Implement the first options-panel shell only: an initially closed, centered, draggable standard client window titled Options with a close button and empty content, toggled with F12. Reuse UiWindowFactory/UiWindowManager; make the shell available before login and across character selection/gameplay/offline states. No settings controls, design-PDF changes, commits or PR in scope. User requested updating to merged PR #2621; feature/client-options-window is now fast-forwarded to origin/develop d9d60831a, with options edits and untracked design deliverables restored without conflicts. Verified outcome: OptionsWindow.cs and empty Options.xml reuse UiWindowFactory and UiWindowManager. Centered 640×440 standard draggable frame, close button, initially closed and non-persisted; global scope stays available across login/selection/gameplay/offline. F12 event handlers suppress key repeat, toggle and raise the window; disposal unsubscribes and unregisters it. Composition registers the shell with owned lifecycle resources. Nine OptionsWindowTests cases exercise real engine input dispatch and GUI layout/mouse input. Combined options/presenter/factory/layout/view-distance regression selection: 43 passed. Non-automation Release client build: zero warnings/errors. git diff --check passed; merged #2621 baseline confirmed as ancestor. Initial parallel build output collision resolved by -m:1 and consistent EnableClientAutomation=true test properties; no source failure. Native graphical client was not launched, so visual smoke remains unverified. No settings controls, commits or PR; design files preserved.