feat(curiocity): make max turns configurable

[shin4141]

Summary

• add optional maxTurns to Curiocity case configuration
• add a --max-turns CLI override and show the resolved value in dry-run output
• carry the value through the matrix and TrialSpec into InteractionEngine
• preserve the existing 100-turn engine default when the option is unset

Why

Curiocity already accepts maxTurns in InteractionEngine, but no configuration or CLI path could supply it. Long-running trials therefore always used the hard-coded default even when their wall-clock timeout was configured independently.

Validation

• npm test — 432 passed
• npm run lint
• npm run build
• node dist/cli.js run --source test/fixtures/cases --max-turns 7 --dry-run

Fixes #260

AI assistance

AI assistance was used to inspect the issue, implement the focused change, and run validation. I reviewed the complete diff.