[runyaga]

D4b: native disk workspace backing (VM).

• Owned host-directory backing for sandbox workspaces through core's native mount service, driven through public snapshots with policy interception; retained until free/dispose with independent cleanup; read-only handling; cap integration; bounded transfer sessions with the persistent-backing adapter rules; web refusal.
• N1-N7, disk parity scenarios, sleep/future dispatch regressions and cwd/lifetime cases as named tests; 21 mutants killed. CI loads the real native library (shared artifact) and records its identity.
• No public name or member change (facade stays 51). No deleted handler restored. Child checkout wiring is D5.
• Floors and baselines untouched.

Pre-PR review: independent high-effort review, reviewed at 44474ab
DCM host gate: GREEN at the final head.

[runyaga]

Draft: independent review is paused until the reviewer quota resets; not ready for merge.