Address review feedback on PR #1268: - setActiveWorkstream now uses planningRoot(cwd) instead of hardcoded path, matching getActiveWorkstream for consistency - Add 33 path traversal rejection tests covering all entry points: CLI --ws flag, GSD_WORKSTREAM env var, cmdWorkstreamSet, and poisoned active-workstream file Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>