refactor: reverse Core↔Differential dependency and make all components independent

[JusterZhu]

Problem

The current project dependency structure is backwards:

• GeneralUpdate.Differential depends on GeneralUpdate.Core — but Differential is the low-level diffing engine and Core is the higher-level orchestrator
• ICleanStrategy/IDirtyStrategy/IBinaryDiffer are defined in Core but are Differential concepts
• Bowl/Drivelution/Extension unnecessarily depend on Core even though they only use basic utilities (logging, file operations)

Solution

See PR #446

Key changes:

1. Reverse Core↔Differential dependency: Core now references Differential
2. Move orchestration types from Differential to Core (DefaultCleanStrategy, DiffPipeline, etc.)
3. Make Differential a pure algorithm library (IBinaryDiffer + implementations only)
4. Make Bowl/Drivelution/Extension fully independent (zero project references)
5. Remove ICleanStrategy from Core.Differential namespace

Final dependency graph:

Differential (0 deps) ← Core (1 dep) 
Bowl (0 deps) | Drivelution (0 deps) | Extension (0 deps)

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