Implement Expected Exit Codes Configuration

[alexmond]

Feature Request: Expected Exit Codes

Add support for configuring which exit codes are considered expected vs unexpected.

Requirements

• Add exitcodes field to ProcessConfig (Set, default: [0])
• Modify process monitoring to check against expected codes
• Integrate with auto-restart policy (UNEXPECTED mode)
• Add events for expected vs unexpected exits

Acceptance Criteria

• Exit codes in exitcodes set are treated as expected/successful
• Auto-restart UNEXPECTED mode only restarts on unexpected exit codes
• Process events clearly indicate expected vs unexpected termination