[TASK][Timpani-n] Support mixed-criticality task sets

[LGSI-KarumuriHari]

📝 Task Description

Handle tasks with different criticality levels in the same system.

📋 Checklist

• Define criticality levels (e.g., low, medium, high, critical)
• Implement criticality-aware scheduling
• Allocate resources based on criticality
• Handle mode changes (degraded operation)
• Protect high-criticality tasks
• Document criticality handling strategy

🔗 Related Requirement

Relates to #25 (Task Management)
Relates to #16 (Implement Task Management)

📐 Implementation Guidelines

• Functional Requirement: FR-2.3.3 - Support mixed-criticality task sets
• Component: timpani-n/Execution Layer/Task Manager
• Assign higher priorities to critical tasks
• Implement mode change protocol for overload
• Protect critical tasks during degraded mode
• Drop or defer low-criticality tasks if needed

🧪 Testing Method

• Unit test: Verify criticality assignment
• Integration test: Test mode changes under overload
• Safety test: Ensure critical tasks always meet deadlines