ci: increase Claude Code max-turns to 20

[YuminosukeSato]

Summary

Increase the maximum number of turns for Claude Code reviews from 5 to 20.

Problem

Opus 4.6 is hitting the 5-turn limit during code reviews. Recent PR review (PR #90) used 6 turns:

{
  "subtype": "error_max_turns",
  "num_turns": 6,
  "total_cost_usd": 0.13078
}

Changes

- claude_args: "--max-turns 5 --model claude-opus-4-6"
+ claude_args: "--max-turns 20 --model claude-opus-4-6"

Benefits

More Comprehensive Reviews

Opus 4.6 performs deeper analysis than Sonnet 4.5:

• Security analysis - More thorough UDS security checks, HMAC validation
• Architectural insights - Better understanding of IPC patterns and performance implications
• Error detection - More accurate identification of Go error wrapping issues

Why 20 Turns?

• Opus needs more time - Complex analysis requires multiple reasoning steps
• Thorough reviews - Allows complete analysis without artificial cutoffs
• Cost-effective - Better to complete one thorough review than restart multiple times

Cost Implications

• Per turn cost: ~$0.02 (based on observed $0.13 for 6 turns)
• Max cost per PR: ~$0.40 (20 turns)
• Average expected: ~$0.15-0.25 (7-12 turns)

Trade-offs

• ✅ More thorough code reviews
• ✅ Better architectural insights
• ✅ Fewer incomplete reviews
• ❌ Potentially higher API costs per PR
• ❌ Longer review times

Verification

After merging, Claude Code will be able to complete reviews without hitting turn limits.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR increases the maximum number of turns for Claude Code reviews from 5 to 20 to prevent incomplete reviews. The change was motivated by Opus 4.6 hitting the turn limit during PR #90, which required 6 turns but was capped at 5.

Changes:

• Increased --max-turns parameter from 5 to 20 in the Claude Code workflow configuration

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