resolve cross-list duplicate citations in edge extraction

[vvivekranjan]

Summary

This PR fixes a bug in resolve_extracted_edge where valid duplicate edge citations identified by the LLM within existing_edges (invalidation candidates) were incorrectly discarded by the duplicate-range guard. The duplicate index validation has been expanded to support the entire continuous index space (up to max_valid_idx), allowing cross-list duplicates to be correctly mapped, resolved, attributed, and saved rather than leaked as new duplicate edges.

Type of Change

• Bug fix
• New feature
• Performance improvement
• Documentation/Tests

Objective

N/A - Bug fix

Testing

• Unit tests added/updated
• Integration tests added/updated
• All existing tests pass

Breaking Changes

• This PR contains breaking changes

Checklist

• Code follows project style guidelines (make lint passes)
• Self-review completed
• Documentation updated where necessary
• No secrets or sensitive information committed

Related Issues

Closes #1672

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[vvivekranjan]

I have read the CLA Document and I hereby sign the CLA behalf on myself, e-mail: vvivekranjan20@gmail.com