Add JSON error handling to community_stars.py

[Copilot]

Summary

Adds json.JSONDecodeError handling when loading GitHub contributor data. Previously, malformed JSON would cause an unhandled exception instead of a helpful error message.

try:
    with open(github_data_file, 'r') as f:
        contributors_data = json.load(f)
except FileNotFoundError:
    # existing handler
except json.JSONDecodeError as e:
    print(f"Error: Invalid JSON in {github_data_file}")
    print(f"Details: {e}")
    print("Please ensure the file contains valid JSON from the GitHub API.")
    sys.exit(1)

Type of Change

• Bug fix
• Code quality

AI Assistance

• This PR was created or reviewed with AI assistance

Testing

Tested with malformed JSON, valid empty JSON, and missing file scenarios. All error paths produce appropriate messages.

Related Issues

Relates to #5776
Discussion: #5776 (comment)

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