Allow move-only commands for fixed-size Windows windows

[martinbha]

Problem

The Windows adapter rejects every window without WS_THICKFRAME, including windows that can move but cannot resize.

WS_THICKFRAME indicates resize support; it does not mean the window is immovable. The current check prevents fixed-size dialogs and application windows from using move-only commands such as Center, Move Left, Move Right, Move Up, and Move Down.

The shared runtime intentionally lets each native adapter handle non-resizable windows, and the macOS adapter already preserves the allowed size while aligning constrained windows within the requested zone.

Proposed change

• Do not reject a window solely because it lacks WS_THICKFRAME.
• For move-only commands, preserve the current width and height and apply the requested position.
• For layout commands that request a different size, preserve the actual fixed size and align it within the requested zone and destination work area.
• Continue rejecting hidden, minimized, shell, child, and tool windows as appropriate.
• Return the actual applied rectangle so history remains accurate.

Acceptance criteria

• Center and directional Move commands work for movable fixed-size Windows windows.
• Fixed-size windows remain within the destination work area.
• Resizable windows retain their current behavior.
• Tests cover move-only and tiling requests for a non-resizable window.
• The Windows application target passes check and Clippy.