chore(m170): open — zero-trust lease sandbox, on M136's branch

Indy's call: one tree, one branch. M170 does not supersede M136's
HOME fix — they close different failure classes. M136 makes leases
run at all; M170 makes them safe to run. The live proof needs both,
so they share a branch and the same Pull Request.

Baseline carried from the HOME fix's own run: unit=4166
integration=709.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>