## What changed
Compute the `sandbox_policy` label for `codex.conversation_starts` from the effective `PermissionProfile` without constructing a legacy `SandboxPolicy`. Preserve the historical labels and native-path compatibility fallbacks, including `workspace-write` for writable profiles that cannot be represented by a legacy policy.
Share the full-disk write compatibility check with session startup and the write-intent check with legacy policy conversion.
## Testing
Extend telemetry tests to assert sandbox labels in both logs and traces across disabled, external, read-only, workspace-write, and full-disk profiles, including unrenderable writable URIs and read restrictions. Add protocol assertions for legacy write-intent detection.
GitOrigin-RevId: 00f11d763c366453e7bb0899546a4ebbdb93c4d5