Rename claude-4.6-opus to claude-opus-4-6

[juanmichelini]

Summary

Rename claude-4.6-opus to claude-opus-4-6 to match Anthropic's official branding.

Changes

• Rename results directory from claude-4.6-opus to claude-opus-4-6
• Update metadata.json model and directory_name fields
• Update Model enum and mappings in validate_schema.py

Fixes #538

@juanmichelini can click here to continue refining the PR

[github-actions]

📊 Progress Report

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OpenHands Index Results - Progress Report
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Target: Complete all model × benchmark pairs
  11 models × 5 benchmarks = 55 pairs
  (each pair requires all 3 metrics: score, cost_per_instance, average_runtime)

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OVERALL PROGRESS: ⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛ 100.0%
  Complete: 55 / 55 pairs
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✅ Schema Validation

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Schema Validation Report
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Results directory: /home/runner/work/openhands-index-results/openhands-index-results/results
Files validated: 28
  Passed: 28
  Failed: 0

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VALIDATION PASSED
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This report measures progress towards the 3D array goal (benchmarks × models × metrics) as described in #2.

[juanmichelini]

Closing will do one big PR.