feat: Add interactive submit-project script for custom challenges

[ret2libc]

Implements issue #220 by adding an interactive submit-project script that guides users through submitting custom challenges.

Features:

• Extended challenge.py with submit-project subcommand
• Interactive questionnaire following specified requirements
• OSS-Fuzz project URL discovery using grep (no yaml import)
• Support for diff mode (..) and full mode analysis
• Automatic default branch detection
• Added Makefile target for easy access
• Validates user input and provides helpful feedback

Closes #220

Generated with Claude Code

[ret2libc]

@claude address the review

[claude]

Claude finished @ret2libc's task —— View job

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Todo List

• Read the challenge.py file to understand current implementation
• Identify grep/sed usage around line 552 mentioned in review
• Replace shell commands with equivalent Python code
• Test the changes if possible
• Commit and push the fixes

Changes Made

Replaced the shell command approach in get_project_git_url_from_oss_fuzz() with pure Python:

• Before: Used bash -c with grep -E '^main_repo:' and sed 's/main_repo: *//g'
• After: Uses Python file reading with regex parsing via re.match()
• Improvements:
  • Proper temporary directory management with tempfile.mkdtemp()
  • Better error handling for file operations
  • More robust regex pattern for parsing YAML values with/without quotes
  • Cleaner resource cleanup

The function now parses the project.yaml file line by line looking for main_repo: entries and extracts the URL value using a regex pattern that handles both quoted and unquoted values.

✅ Review feedback addressed! The grep and sed commands have been replaced with pure Python code as requested. Changes committed and pushed to the PR branch.

[ret2libc]

• Move this logic into buttercup-ui, so it can be triggered from the UI and we can keep everything in one place.