fix(eval): use percentages in evaluation summary

[christso]

Summary

• Changed evaluation summary to display scores as percentages (e.g., 75%) instead of decimals (e.g., 0.750), matching the per-test progress log format
• Updated threshold display in verdict line (e.g., >= 80% instead of >= 0.8)
• Updated histogram bin labels to use percentage ranges (e.g., 0%-20% instead of 0.0-0.2)

Before:

RESULT: FAIL  (2/5 scored >= 0.8, mean: 0.594)
Mean score: 0.594
Score distribution:
  0.0-0.2: 0
  0.2-0.4: 1

After:

RESULT: FAIL  (2/5 scored >= 80%, mean: 59%)
Mean score: 59%
Score distribution:
  0%-20%: 0
  20%-40%: 1

Test plan

• All existing tests updated and passing (179 eval/compare tests, 1618 core tests, 67 eval package tests, 443 CLI tests)
• Integration test updated for new format
• Matrix summary test updated for new format

🤖 Generated with Claude Code

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