[Engine] TriggerPolicy cadence execution and interval reset

[learncold]

Summary

• Wire SystemDescriptor.triggerPolicy into SystemScheduler::executePhase() so phase execution now evaluates descriptor-owned cadence instead of relying on runtime call-site filtering.
• Add deterministic Interval cadence support with intervalTicks, including scheduler-owned cadence state that resets on initialize() and stop().
• Extend scheduler/runtime tests and update the runtime UML explanation so the implementation matches the documented engine contract.

Related Issue

• Closes Task-TriggerPolicy 실행 조건과 Interval cadence 적용 #95

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
• Additional checks:
• cmake --preset windows-debug-no-app
• cmake --build --preset build-no-app-debug
• ctest --preset test-no-app-debug --output-on-failure

Risks / Follow-up

• Interval currently fires on the first applicable phase tick and then repeats every intervalTicks; if the engine later needs offset-aware cadence, that should be introduced as an explicit descriptor field rather than hidden scheduler behavior.