Add Process Grouping (like supervisord [group:])

[alexmond]

Feature Request: Process Dependencies

Add support for process dependencies to control startup order.

Requirements

• Add dependsOn field to ProcessConfig (list of process names)
• Add priority field for startup ordering (lower numbers start first)
• Implement dependency resolution algorithm
• Detect circular dependencies and fail fast
• Handle dependency failures (stop dependent processes)

Acceptance Criteria

• Processes start in correct dependency order
• Circular dependencies are detected and rejected
• When a process fails, its dependents are stopped