plan: deep audit implementation (chunked Workflow script + gates)

9-task plan implementing the spec at
planning/specs/2026-06-07-deep-audit-design.md. Single parametrized
Workflow script at planning/audit/workflow.mjs runs each chunk; user
gates between chunks; final merge as a one-shot Opus Agent.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: lesnik512