Add JSON schema validation for pipeline.config.json

[PAMulligan]

Summary

pipeline.config.json is a 500+ line configuration file that controls pipeline behavior, thresholds, iteration limits, app-type definitions, and orchestration settings. There is no schema validation, making it easy to introduce typos or invalid values that cause silent failures.

Problems

• No way to validate config changes before running the pipeline
• Typos in field names (e.g., maxAgedays vs maxAgeDays) go undetected
• No IDE autocompletion or hover docs for config fields
• No validation that referenced phases exist in the orchestration graph
• No type checking on threshold values (e.g., negative coverage percentages)

Acceptance Criteria

• JSON Schema file (pipeline.config.schema.json) covering all config sections
• Schema includes descriptions for non-obvious fields (e.g., regionGridSize, maxConcurrent)
• Validation script or integration that checks config against schema
• Schema referenced in pipeline.config.json via $schema field for IDE support