Feat/cache jq filters

[timmilesdw]

Overview

Architectural overhaul of the shell-operator filter system that introduces pre-compilation of JQ expressions during configuration, eliminating runtime compilation overhead. The refactoring replaces the complex interface-based design with a simplified functional approach and consolidates all filtering logic.

Key changes:

• Performance: JQ expressions now compiled once at configuration time instead of on every filter operation
• Architecture: Replaced Filter interface with functional Run(expression, filterFn, obj) API
• Consolidation: Consolidated pkg/filter/jq/ subdirectory into main pkg/filter/ package
• Precedence: Implemented explicit filter precedence: custom filter function > JQ expression > no filter
• Testing: Added comprehensive test suite covering all scenarios

Benefits:

• Simplified architecture and maintenance
• Clear filter precedence rules
• Consolidated codebase
• 100% backward compatibility maintained

Special notes for your reviewer

Internal refactoring - no breaking changes. Major code simplification while preserving functionality.