Add support for setting default script metadata via GENAISCRIPT_DEFAULT_SCRIPT_META environment variable

[Copilot]

This PR implements the ability to set default script metadata globally using the GENAISCRIPT_DEFAULT_SCRIPT_META environment variable, addressing the feature request to configure default metadata values for all scripts from a centralized location.

Problem

Users needed a way to set default metadata values across all their GenAIScript scripts without having to modify each individual script file. This is particularly useful for:

• Configuring environment-specific metadata
• Setting organization-wide metadata standards
• Applying consistent metadata across projects

Solution

Added a new environment variable GENAISCRIPT_DEFAULT_SCRIPT_META that accepts JSON5-formatted script metadata. The implementation includes:

Core Changes

1. New parsing function: parseDefaultMetaFromEnv() in env.ts that safely parses the environment variable as JSON5 and filters to valid PromptArgs fields
2. Template integration: Modified parsePromptScript() in template.ts to merge only the metadata field from environment defaults
3. Priority handling: Environment metadata takes highest priority, overriding script-defined metadata values for the same keys
4. Field filtering: Only valid PromptArgs fields are processed, excluding internal fields like id, jsSource, defTools, and resolvedSystem

Usage Example

# Set default metadata for all scripts
export GENAISCRIPT_DEFAULT_SCRIPT_META='{
  "metadata": {
    "environment": "production",
    "version": "1.0",
    "team": "ai-engineering"
  }
}'

Error Handling

• Gracefully handles invalid JSON with debug logging
• Ignores non-object values without breaking script execution
• Provides clear debug output when DEBUG=genaiscript:config:env is set

Comprehensive Testing

Added extensive test coverage including:

• Valid JSON5 parsing scenarios
• Invalid input handling
• Metadata field merging behavior
• Environment variable precedence rules
• Edge cases and error conditions

The implementation follows existing code patterns and maintains backward compatibility while providing a safe way to set default metadata across all scripts without affecting other script properties.

---

Additional instructions:

Add a function in env.ts that parses the GENAISCRIPT_DEFAULT_META as a JSON payload of PromptScript metadata. This metadata should get merged last into the main script metadata object. Add logging.

Fixes #1924

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.

[pelikhan]

@copilot rename GENAISCRIPT_DEFAULT_META to GENAISCRIPT_DEFAULT_SCRIPT_META

[pelikhan]

@copilot only merge metadata fields

[Copilot]

Changed to only merge the metadata field from environment defaults, not all script properties (commit 4d56cde).

[pelikhan]

@copilot only return fields in promptargs

[Copilot]

Added filtering to only return valid PromptArgs fields, excluding internal fields like id, jsSource, defTools, and resolvedSystem (commit 4d56cde).

[Copilot]

@copilot rename GENAISCRIPT_DEFAULT_META to GENAISCRIPT_DEFAULT_SCRIPT_META

Renamed the environment variable from GENAISCRIPT_DEFAULT_META to GENAISCRIPT_DEFAULT_SCRIPT_META across all implementation files and tests (commit 50354b5).