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[5_state-management] add signal-based global and feature stores
Add scenario builder dialog UI and language pair profile (G0–G1).
Implement language pair support for cards, catalog, scenarios, and learning (G2–G5).
Add G11 courses, lessons, and learning flow.
Show all enabled phonetic systems and seed ru→zh demo cards.
Implement G7 multi language pairs with one active pair at a time.
[TEME]