feat: Refactor CLI to read from stdin and output JSON

[dsillman2000]

CLI I/O Mode Change

Overview

Refactored the CLI tool to output JSON instead of YAML for better interoperability and deterministic formatting. For consistency, the tool now reads exclusively from stdin and writes to stdout.

Changes Made

1. Output Format Changed

• Before: Outputs YAML with ruamel.yaml formatting
• After: Outputs JSON with sorted keys and 2-space indentation

2. Simplified Interface

• Removed file I/O arguments (-i/--input, -o/--output)
• Now reads exclusively from stdin and writes to stdout
• Eliminated dependency on ruamel.yaml

Benefits

1. Deterministic Output: JSON provides consistent key ordering
2. Interoperability: JSON is widely supported across programming languages
3. Simplified Usage: Single-purpose tool (stdin -> stdout)
4. Reduced Dependencies: Removes ruamel.yaml dependency

Usage Example

# Before
yref-compile -i input.yaml -o output.yaml

# After
cat input.yaml | yref-compile > output.json

Testing

The core functionality remains unchanged - only the output format differs. The !reference tag resolution logic in YAMLReference class is unaffected.