Motivation

The current multi-agent resource allocation uses slot-based configuration with complex _calculate_device_slot_* methods that tightly couple slot calculation with allocation modes. Before implementing the new device-based approach from BEP-1041, we need to establish a clean baseline by removing this complexity. This allows us to incrementally rebuild the partitioning logic with the new device-centric design.

Required Features

• Remove _calculate_device_slot() dispatch method from ResourceAllocator
• Remove _calculate_device_slot_shared() method
• Remove _calculate_device_slot_auto_split() method
• Remove _calculate_device_slot_manual() method
• Make AUTO_SPLIT and MANUAL modes fall back to SHARED behavior (all agents see all devices)
• Remove or skip tests that verify partitioning behavior (they will fail until restored in later tickets)

Impact

• src/ai/backend/agent/resources.py - ResourceAllocator class
• tests/unit/agent/test_resource_allocation.py - Tests for removed functionality

Testing Scenarios

1. SHARED mode unchanged: Verify SHARED mode continues to work as before (all agents see all devices)
2. AUTO_SPLIT fallback: Verify AUTO_SPLIT mode now behaves like SHARED (no partitioning)
3. MANUAL fallback: Verify MANUAL mode now behaves like SHARED (no partitioning)
4. No runtime errors: Verify agent starts successfully with each allocation mode

JIRA Issue: BA-4143