Decouple SetupStep into Specific Steps #302

Goal

The current PreFlightStep (previously SetupStep) is a 'God Step' that handles too many responsibilities: file validation, asset injection, and setup/compilation commands. This issue proposes decomposing it into granular, single-responsibility steps to improve pipeline clarity, error reporting, and resource efficiency.

Proposed Changes

1. Decomposition of PreFlightStep:
   • FileCheckStep: Validates presence of required files. Moved before SandboxStep to fail fast and save resources.
   • AssetInjectionStep: Handles moving static assets into the sandbox.
   • SetupCommandsStep: Executes compilation and environment setup commands inside the sandbox.
2. Step Categorization:
   • Introduce a category (or step_type) attribute to the Step model to group steps into SETUP, GRADING, and REPORTING.
3. Template Intelligence:
   • Allow Grading Templates to define their own required_files and setup_commands. The pipeline should merge these with the assignment-level configuration.

Task List / Sub-Issues

• Implement category attribute in Step Model and StepRegistry [Pipeline] Implement step category attribute #307
• Create FileCheckStep and move it before SandboxStep [Pipeline] Create FileCheckStep #308
• Create AssetInjectionStep [Pipeline] Create AssetInjectionStep #309
• Create SetupCommandsStep (replacing remaining PreFlight logic) [Pipeline] Create SetupCommandsStep #310
• Implement Template-level setup requirements (Required Files & Commands) [Pipeline] Implement Template-level setup requirements #311
• Deprecate PreFlightStep and update StepRegistry sequence [Pipeline] Finalize PreFlightStep deprecation #312