[Option B] Consolidate ThreadedStrategy implementation

[danieljsinclair]

Issue

Consolidate ThreadedAudioMode + ThreadedRenderer into unified ThreadedStrategy.

Background

Current architecture has coupled pair that cannot be swapped independently:

• ThreadedAudioMode: Handles lifecycle and simulation updates
• ThreadedRenderer: Handles rendering with cursor-chasing buffer

This creates unnecessary complexity and violates OCP.

Goal

Create ThreadedStrategy that unifies lifecycle and rendering:

• Single class implementing IAudioStrategy
• Uses IAudioHardwareProvider for platform-specific audio
• Handles cursor-chasing logic internally
• Manages circular buffer state

Implementation Plan

1. Create ThreadedStrategy.h/cpp implementing IAudioStrategy
2. Merge ThreadedAudioMode lifecycle methods into ThreadedStrategy
3. Merge ThreadedRenderer rendering methods into ThreadedStrategy
4. Inject IAudioHardwareProvider instead of using AudioUnit directly
5. Manage CircularBuffer internally
6. Maintain cursor-chasing diagnostics

Acceptance Criteria

1. ThreadedStrategy.h/cpp created implementing IAudioStrategy
2. Combines ThreadedAudioMode + ThreadedRenderer functionality
3. Uses IAudioHardwareProvider for audio hardware access
4. Maintains all cursor-chasing behavior (pre-fill, cursor tracking, underrun handling)
5. All tests pass (existing ThreadedRenderer tests)
6. Buffer math verified identical via deterministic tests
7. Clean build with no warnings

Testing

• All existing ThreadedRenderer unit tests pass
• All existing ThreadedAudioMode unit tests pass
• Simulator-level audio tests produce identical output
• No behavioral changes (audio sounds identical)

Dependencies

• CRITICAL: Documentation describes non-existent NEW architecture (IAudioStrategy) #8: Create IAudioStrategy interface
• Remove/accurately document SilentRenderer in architecture docs #9: Create IAudioHardwareProvider interface
• Document actual pull model architecture (modes/renderers/factories) #11: Create CoreAudioHardwareProvider implementation

Related Issues

• Clarify FillSilence location in architecture documentation #10: Consolidate SyncPullStrategy implementation
• Archive and reference historical investigation docs #14: Update CLIMain wiring for IAudioStrategy