[SaladDay]

microsandbox now runs every Environment on external workspace storage (the nfs adapter). Its Provider-owned disk mode is gone from the Provider, its helper, Core, Web, the generated projections, the node installer, docs and tests. Docker and E2B keep their own disks.

• Protocol: DeploymentPolicy.Workspace present means the Provider runs every Environment on external storage. A deployment of such a Provider with no storage selected returns ErrWorkspaceRequired, reported as 409 workspace_storage_required. environment_disk_mib there is only a capacity quota request (default 0).
• Web: microsandbox setup cannot be saved without workspace storage, and tells the administrator to select it first.
• mcode does not declare retained_native_history, so the existing rule rejects it on microsandbox. The rejection is now sessions.ErrRetainedHistoryUnsupported, reported as 400 unsupported_or_invalid_configuration with the reason instead of the generic invalid-request message; the compatibility record and Session admission table say so.
• The node installer creates oac-node with Core's UID 65532 and stops with nothing changed when another account holds that UID or an existing oac-node uses another UID. The manual precreate step is gone from the docs.
• The microsandbox wire protocol version is 7.

Checks: Core go vet ./...; go test for sandbox, deployment, deploymentpg, execution, api, cmd/server and the whole integration package (its Worker fixture now builds workspace storage as cmd/server does); helper tests with the bundled SDK (scripts/build-microsandbox-provider.py test); pytest deploy/node; agents-client typecheck and tests; Web typecheck and sandbox/i18n tests; translation check. Real-cluster run on mx (together with #816): 409 before storage is selected, the Web hint, oac-node adopted with UID 65532, Codex and Claude Code hosted acceptance 9/9 each, preparation cache and resume probes correct. Playwright cases run in CI only (no browser on the dev server).

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