Add Variable Resolution in Source Paths and New Path Variables

[butschster]

This PR enhances CTX's variable system by enabling variable resolution in source paths and adding new predefined path variables. This makes configurations more flexible, reusable, and suitable for multi-environment setups.

Changes

1. Variable Resolution in Source Paths

Source paths now support variable substitution, allowing dynamic path construction:

Before:

documents:
  - description: "API Documentation"
    sources:
      - type: file
        sourcePaths:
          - "src/Controllers"  # Static path only

After:

variables:
  env: production
  src_dir: src/{{env}}

documents:
  - description: "API Documentation"
    sources:
      - type: file
        sourcePaths:
          - "{{src_dir}}/Controllers"  # Dynamic path based on environment
          - "${ROOT_PATH}/config" # Using predefined variables

2. New Predefined Path Variables

Added four new predefined variables for project paths:

Variable	Description	Example
${ROOT_PATH}	Project root directory	/home/user/my-project
${CONFIG_PATH}	Configuration file path	/home/user/my-project/context.yaml
${ENV_PATH}	Environment file path	/home/user/my-project/.env.local
${BINARY_PATH}	CTX binary path	/usr/local/bin/ctx

[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../Config/Import/PathPrefixer/SourcePathPrefixer.php	0.00%	1 Missing ⚠️

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