[plan] Split checkout_manager.go into state management and step generation

[github-actions]

Objective

Split pkg/workflow/checkout_manager.go (1,005 lines) by moving all step generation functions to a new file, separating state management from YAML step generation.

Context

From discussion #23903 (Repository Quality: File Size Discipline). This file conflates CheckoutManager state management with GitHub Actions YAML step generation. The step generation functions are independently testable and have a natural seam for extraction.

Approach

1. Create pkg/workflow/checkout_step_generator.go in the same package (package workflow)
2. Move these functions to the new file:
   • GenerateCheckoutAppTokenSteps
   • GenerateCheckoutAppTokenInvalidationSteps
   • GenerateAdditionalCheckoutSteps
   • GenerateGitHubFolderCheckoutStep
   • GenerateDefaultCheckoutStep
   • generateCheckoutStepLines
3. Keep CheckoutManager type definition, NewCheckoutManager, all getters/setters, and resolver logic in checkout_manager.go

Rules

• Same package (package workflow)
• Do NOT change any function signatures
• Run make fmt after changes
• Run go test ./pkg/workflow/ -run ".*[Cc]heckout.*" to validate
• Run make agent-finish before committing

Acceptance Criteria

• pkg/workflow/checkout_step_generator.go contains all Generate* / generate* step functions
• pkg/workflow/checkout_manager.go reduced to type definition + state management — under 400 lines
• Both files under 500 lines
• All existing checkout-related tests pass

Generated by Plan Command for issue #discussion #23903 · ◷

• expires on Apr 3, 2026, 2:40 PM UTC

[github-actions]

🍪 Issue Monster has assigned this to Copilot!

I've identified this issue as a good candidate for automated resolution and assigned it to the Copilot coding agent.

The Copilot coding agent will analyze the issue and create a pull request with the fix.

Om nom nom! 🍪

🍪 Om nom nom by Issue Monster · ◷