[Application] prepare Sprint 1 demo happy path

[SilverSupplier]

Summary

• Seed the built-in Demo project with a Sprint 1 baseline scenario, crowd placement, and configured events.
• Polish the Layout Review -> Scenario Authoring -> Run -> Result Summary happy path, including clearer staged/run/result UI states.
• Add demo fixture coverage that verifies the baseline scenario can run to result artifacts.

Related Issue

• Refs EPIC-2 Sprint 1 Demo Vertical Slice #2
• Refs Task-baseline 시나리오 라이브러리와 readiness panel UI 구현 #118
• Refs Task-ControlPlan 운영 이벤트 editor UI 구현 #119
• Refs Task-run queue와 실행 제어 workspace UI 구현 #120
• Refs Task-run 결과 요약과 variation summary analysis UI 구현 #130

Area

• Engine
• Domain
• Application
• Docs
• Build
• Analysis
• Chore

Architecture Check

• I kept the dependency direction application -> domain -> engine.
• I did not add Qt UI code to src/domain.
• I did not add domain or application dependencies to src/engine.
• I used src/ as the include root.

Verification

• cmake --preset windows-debug
• cmake --build --preset build-debug
• ctest --preset test-debug
• Not run (reason below)

Risks / Follow-up

• Manual GUI click-through rehearsal was not automated in this pass.
• Scenario event editing/deletion and persisted result artifacts remain follow-up work.