codex/fix podman isolated dns

[drew]

Summary

Restore policy DNS resolution for isolated Podman workloads, including credential-gated endpoints addressed through host.openshell.internal.

Related Issue

Stability investigation stacked on #3602 and ultimately #3583. The managed Podman job in run 35850241086 exposed this failure.

Changes

• Mount a per-sandbox, read-only resolver file in the network=none workload so libc sends DNS to the sandbox's loopback policy DNS relay.
• Pin the backend's host gateway in the supervisor runtime descriptor. Native Podman uses the supervisor's host-network loopback; Podman Machine uses the configured gateway. Reserved host aliases are then authorized against that pin.
• Clean up the resolver secret with the other Podman sandbox resources and document the isolation behavior.

Testing

• cargo test -p openshell-driver-podman --lib: 224 passed.
• mise run pre-commit: passed.
• mise run ci: passed.
• Local Podman CLI conformance: both scenarios passed.
• Focused local Podman credential_gating E2E: passed (1 test, 96.33s).

Checklist

• Signed-off conventional commit
• Documentation updated
• Full local CI passed
• Focused Podman E2E passed

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[johntmyers]

going to close in favor of #3606