[plan] Fix version field type handling to match schema definitions

[github-actions]

Overview

This tracking issue addresses critical inconsistencies between schema type definitions and runtime type handling for version fields. The schema advertises string | number support with numeric examples, but implementations only handle strings, causing silent configuration failures.

Source: Discussion #8218

Problem Summary

Three version fields accept "type": ["string", "number"] in schema with examples like 20 and 3.11, but runtime parsing only checks for strings:

• engine.version - affects AI engine version pinning
• tools.github.version (GitHub MCP) - affects MCP server versioning
• tools.playwright.version - affects Playwright container versioning

Impact: Users following schema examples have numeric versions silently ignored without errors/warnings, causing unexpected fallback to default versions.

Planned Tasks

1. Fix engine.version numeric type handling in pkg/workflow/engine.go
2. Fix GitHub MCP version numeric type handling in pkg/parser/mcp.go
3. Fix Playwright version numeric type handling in pkg/parser/mcp.go
4. Add regression tests for numeric version values
5. Create reusable version parsing helper function

Success Criteria

• All three version fields accept both string and numeric types as advertised
• Numeric versions (integers and floats) are properly converted to strings
• Regression tests prevent future type handling inconsistencies
• No breaking changes to existing string-based configurations

Risk Assessment

Risk Level: Medium-High

• Silent failures without error messages
• Schema examples actively encourage numeric format
• Low detectability for users

Mitigation: Localized to 3 specific code locations, straightforward fixes using existing patterns in the codebase (e.g., max-turns field implementation).

AI generated by Plan Command for discussion #8218