feat: enable full autograding based on rejection thresholds

[dimasmds]

Summary

• Implement smart draft logic based on rejection count thresholds instead of course ID restrictions
• Remove unused draft field from review result interfaces and methods
• Add comprehensive test coverage for different rejection scenarios
• Enable full autograding for approved submissions regardless of rejection history

Changes Made

• Draft Logic Enhancement: Modified getDraftDecision() in report-generator.ts:46-60 to use rejection count thresholds:
  • Rejections < 3: is_draft = null (full autograding)
  • Rejections ≥ 3: is_draft = true (requires manual review)
  • Approved submissions: is_draft = null (full autograding)
• Special Handling: Added logic for massive rejections (≥5) in report-generator.ts:21-27:
  • Sets empty message and special note for reviewers
  • Ensures intensive review for struggling students
• Code Cleanup: Removed unused draft field from:
  • course-submission-review.ts:43,56
  • review-result.ts:8
• Test Coverage: Added comprehensive test scenarios in report-generator.test.ts:62-239 covering all rejection threshold combinations

Test Plan

• Test rejection count < 3 (both reject and approve scenarios)
• Test rejection count = 3 (both reject and approve scenarios)
• Test rejection count ≥ 5 with special message handling
• Verify all approved submissions result in is_draft = null
• Ensure massive rejection triggering special reviewer notes

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