Pin Claude Code CLI version to 2.0.1 instead of @latest

[Copilot]

Problem

The Claude Code CLI was being installed using @latest version specifier in the generated GitHub Actions workflows. This caused two issues:

1. Lack of reproducibility: Workflows could produce different results across runs as new versions were automatically picked up
2. Potential breaking changes: Updates to Claude Code CLI could introduce breaking changes without warning

Solution

This PR pins the Claude Code CLI version to 2.0.1 (the current latest stable release) by default, while still allowing users to override this via the engine.version field in their workflow frontmatter.

Implementation

Added a DefaultClaudeCodeVersion constant in pkg/constants/constants.go and updated the Claude engine to use this pinned version instead of hardcoded "latest":

// Before
version := "latest"
if workflowData.EngineConfig != nil && workflowData.EngineConfig.Version != "" {
    version = workflowData.EngineConfig.Version
}

// After
version := constants.DefaultClaudeCodeVersion  // "2.0.1"
if workflowData.EngineConfig != nil && workflowData.EngineConfig.Version != "" {
    version = workflowData.EngineConfig.Version
}

This generates workflow steps like:

- name: Execute Claude Code CLI
  run: |
    npx @anthropic-ai/claude-code@2.0.1 --print ...

Pattern Consistency

This follows the established pattern in the codebase for other tools:

• GitHub MCP server: pinned to sha-09deac4
• Playwright: uses latest by default but supports version override

User Control

Users can still specify a custom version in their workflow frontmatter:

---
engine:
  id: claude
  version: v1.2.3  # Override the default
---

Testing

• All unit tests updated and passing
• All workflow files recompiled with the new pinned version
• Manual verification of generated workflows
• Custom version override tested and confirmed working

Original prompt

---

This section details on the original issue you should resolve

<issue_title>claude code version should be pinned instead of "@latest"</issue_title>
<issue_description>In the "Execute Claude Code CLI" step, the claude code CLI version should be pinned</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #1126

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[pelikhan]

@copilot use default version strong