fix(editor): normalize documentation and harden editor utilities

[VPDPersonal]

Summary

• Normalize Editor XML documentation for public/protected API, remove XML from internal/private declarations, and keep ordinary C#/USS/UXML comments only where they explain non-obvious behavior.
• Fix generic constraint filtering (Nullable<T> under struct, abstract classes under new()), validate reflected members before reading them, and copy assigned excluded-folder arrays so external mutation cannot bypass persistence and notifications.
• Block keyboard adjustments/deletion of hidden navigation targets, guard invalid dot-grid dimensions that could hang the Editor, and clear inspector-header hover accents after its status changes to None.

Notes for review

Most of the 201 changed files contain documentation/comment cleanup. Behavior fixes include focused regression coverage; the invalid dot-spacing case is guarded in code without a live regression test that would hang the old implementation.

Validation: all 398 EditMode tests passed in Unity 6000.4. Roslyn XML/cref and documented-parameter checks passed across 212 C# files; git diff --check passed. USS/UXML content excluding comments and whitespace is unchanged.

🇷🇺 Кратко

• XML-документация Editor приведена к правилам публичного API; XML у внутренних типов и непубличных членов удалён. Обычные комментарии оставлены для неочевидного поведения.
• Исправлены generic-ограничения, проверка членов перед чтением через reflection и копирование массива исключённых папок.
• Исправлены клавиатурные действия над скрытыми элементами, зависание сетки точек при некорректных параметрах и сброс подсветки заголовка после смены статуса.