Fix fork contribution detection using contributors API

[Mohd-Mursaleen]

PR Description

Fixes the fork contribution detection logic that was missing legitimate open source contributions.

Fixes #149

How the Fix Works

The standard open source workflow is: fork repository → make changes → create PR → get merged. However, the current system was skipping all forks with low fork counts, completely missing these contributions.

The Problem: When a developer contributes to a major project like React, they fork it to their account, make changes, and submit a PR. Their fork typically has 0 forks (it's just a working copy), so the old logic skipped it entirely.

The Solution: Instead of checking the fork's popularity, we now check if the developer actually appears in the original repository's contributors list. If they do, we count it as a legitimate open source contribution using the original repo's significance (stars/forks).

Flow Diagram

Before (Broken):
User Repos → Find Fork → fork_count < 5? → SKIP → Miss Real Contribution

After (Fixed):
User Repos → Find Fork → Get Original Repo → Check Contributors → User Found? → Count as Open Source

Changes Made

• For forks: Check if user appears in original repo's contributors list
• For regular repos: Keep existing contributor count logic
• API Usage: Use /repos/{owner}/{repo}/contributors to verify actual contributions
• Scoring: Use original repository's stats (stars/forks) instead of fork's stats

Example Impact

• Before: Developer's React fork (0 forks) → SKIPPED
• After: Developer found in React contributors → Counted as contribution to 86k star project

This ensures developers following proper open source workflow get fair credit for their contributions.

Testing & Validation

Smoke Tests Performed:

• ✅ PDF to Markdown extraction
• ✅ Section extraction to JSON Resume
• ✅ GitHub enrichment with fork detection on test username
• ✅ Evaluation to JSON with required fields

Provider Testing:

• ✅ Tested with Ollama using default local model
• ✅ Verified GitHub API integration with real fork scenarios

Manual Validation:

• ✅ Ran CLI on sample resumes with fork repositories
• ✅ Verified proper classification of open source vs personal projects
• ✅ Confirmed API error handling and fallback behavior

[Mohd-Mursaleen]

@sp2hari @anxkhn-hacker
Review please.