## What changed
- Add the effective permission profile as `sandbox_mode` in turn metadata for regular, prewarm, compaction, and detached memory requests.
- Reserve `sandbox_mode` so client-provided metadata cannot override the computed value.
## Testing
- Cover metadata headers and request bodies for read-only and danger-full-access modes.
GitOrigin-RevId: 13c690cc99bc2691023f281ca527af049bb1286f