[KeyffMS]

Addresses #121 and #122.

Changes:

• exposes SettingsCoordinator.Current as IReadOnlySightAdaptSettings while retaining defensive-copy behavior;
• changes configuration/runtime read paths to consume read-only snapshots;
• introduces one lightweight SettingsUseCaseContext for shared snapshot/event/commit plumbing across configuration and visual-profile use cases;
• consolidates Commit and PersistCurrent through one private transaction/persistence execution path;
• preserves the rule that only successful Commit publishes Changed, while PersistCurrent does not;
• keeps unexpected failures reported and rethrown;
• adds tests for the read-only public contract and PersistCurrent event behavior;
• updates architecture documentation.

No repository abstraction, generic command framework or inheritance hierarchy is introduced.