Remove tracked PDF and gitignore papers directory

[igerber]

Summary

• Remove papers/2508.21536v2.pdf from git tracking (was accidentally committed)
• Add papers/ to .gitignore to prevent future PDF commits
• Local paper files are preserved, just no longer version-controlled

Methodology references (required if estimator / math changes)

• N/A — no methodology changes

Validation

• Tests added/updated: No test changes (repo hygiene only)
• Backtest / simulation / notebook evidence: N/A

Security / privacy

• Confirm no secrets/PII in this PR: Yes

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Generated with Claude Code

[github-actions]

Overall assessment: ✅ Looks good

Executive summary

• No methodology, estimator, or statistical output changes in this PR.
• Change is limited to repo hygiene: ignore papers/ and remove a tracked PDF.
• No edge-case, inference, or control-group logic touched.
• No tests required for this change.

Methodology

• No findings. This PR only updates .gitignore and removes a binary PDF. No estimators, math, weighting, SEs, or assumptions affected.

Code Quality

• No findings. Simple, scoped change in .gitignore (.gitignore:L82-L88).

Performance

• No findings.

Maintainability

• No findings. Ignoring papers/ helps avoid accidental large binary commits (.gitignore:L82-L88).

Tech Debt

• No findings.

Security

• No findings. Removing a tracked binary reduces accidental distribution risk; no secrets exposed.

Documentation/Tests

• No findings. No code behavior changed; tests not needed.