Extract four helper functions from cmdStepRead to reduce cognitive
complexity from 27 to ≤15:
- loadStepDetail: Load and validate step detail node
- loadTurnData: Load all turn nodes and extract content
- selectTurnsForQuota: Select turns within quota (≥1 always shown)
- formatStepMarkdown: Assemble final markdown output
All 6 existing tests pass. Zero Biome warnings. CLAUDE.md compliant.
Fixes#487