Add relative mouse movement (move by delta)

[JE-Chen]

Summary

Round-11, automation-core. The mouse wrapper exposed only absolute set_mouse_position — no moveRel(dx, dy) (pynput/PyAutoGUI staple) for relative-pointer / canvas / FPS apps and incremental drags.

Layers

• Headless core: je_auto_control/utils/mouse_relative/mouse_relative.py — relative_target (pure current+delta arithmetic), move_mouse_relative (reads live position, moves by delta; injectable getter/setter; raises AutoControlMouseException if position unreadable). No PySide6.
• Facade: both re-exported + __all__.
• Executor: AC_move_mouse_relative.
• MCP: ac_move_mouse_relative (SIDE_EFFECT_ONLY).
• Script Builder: one CommandSpec under Mouse.

Tests / docs

• test/unit_test/headless/test_mouse_relative_batch.py — 6 headless tests (arithmetic, current+delta via injected get/set, unreadable-position raises + wiring + facade). No real pointer.
• EN/Zh feature docs v120_features_doc.rst + toctrees; 3 WHATS_NEW entries.

Note: horizontal mouse-wheel scroll is intentionally deferred — it needs cross-platform backend HWHEEL support that isn't headless-testable. Codacy may show action_required from its coverage gate only (issues=0).

[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

See analysis details on SonarQube Cloud