Add advanced spawn options wrapper with streaming support

[konard]

Goal: Beat cross-spawn's 102M weekly downloads by providing everything they do plus streaming

Missing in cross-spawn:

• No streaming support (only buffered)
• No template literals syntax
• No built-in commands
• No virtual commands
• No real-time output processing

Implementation:

• Template literal syntax ($cmd``)
• Built-in cross-platform commands
• Virtual commands engine
• Add cross-spawn compatibility wrapper: $.spawn() method
• Document migration path from cross-spawn
• Add benchmarks showing our performance advantage
• Create examples showing streaming benefits over buffering

Success Metrics:

• Migration examples for top 10 cross-spawn use cases
• Performance benchmarks (streaming vs buffering)
• Bundle size comparison (~20KB vs ~2KB)
• Feature comparison documentation