Add window tiling/layout geometry planner (halves, grids, cascade)

[JE-Chen]

Compute where to place application windows. save/restore_window_layout replay exact saved positions and snap_window moves one window to a half/quarter — nothing computes a fresh multi-window layout.

• tile_rect (AC_tile_rect): rectangle for a named slot of the screen work area — halves, quadrants, thirds (left_third …), center, full. gap insets all sides. Returns a WindowRect (.as_tuple() / .to_dict()).
• grid_rects (AC_grid_rects): one rectangle per cell of an R×C grid, row-major.
• cascade_rects (AC_cascade_rects): count staggered, overlapping rectangles clamped to the screen (size defaults to 60% of the work area).
• available_slots() lists the slot names; unknown slot / non-positive grid dims raise ValueError. Executor screen arg defaults to the live primary screen.
• Pure geometry: cross-platform, no device dependency, fully headless-testable; composes with any window-move backend. Wired through all 5 layers (core/facade/executor/MCP/Script Builder under Window) + headless test + EN/Zh docs + WHATS_NEW. Qt-free.

[codacy-production]

Not up to standards ⛔

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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