docs: add synchronization notes between docs/Idea.md and docs/todo.md

[Neoplayer]

Motivation

• Reduce duplication of task state between documentation files by establishing docs/todo.md as the primary source of open tasks and keeping docs/Idea.md focused on implementation status and strategic context.
• Clarify the update workflow so roadmap entries remain consistent with current priorities and task statuses.

Description

• Added a "Синхронизация с docs/todo.md" subsection to 22.1) Текущее состояние that states docs/todo.md is the primary source of Stage A tasks, explains that docs/Idea.md should not duplicate the full todo list, and instructs updating docs/todo.md first then reflecting results in Idea.md.
• Added a "Принцип roadmap-синхронизации с docs/todo.md" subsection to 22.2) Перспективы that documents the intended workflow of updating priorities in docs/todo.md before adjusting the roadmap and clarifies that the roadmap should map todo tasks to stages and dependencies.

Testing

• No automated tests were run for this documentation-only change.

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Codex Task