Implements 4 completed tickets + partial progress on 2 more: - #93 Tier marker components (ActiveSim, BackgroundSim, StateSaved + TierPlugin) - #138 Information tag schema (ObserverAccess enum in knowledge/types.rs) - #124 Sound event system (SoundEventEmitter, SoundEventQueue, bridge wiring) - #193 Line previewer CLI (line_preview binary with filter/explain/sequence modes) - #94 Active tier simulation (in progress — With<ActiveSim> filters) - #139 Component-level access control (in progress — filter_by_access) Updates snapshot fixtures and test golden files for new sound_events field. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>