feat(podman): isolate workloads behind the host supervisor

[drew]

Summary

Add the Podman implementation of the RFC 0012 sandbox/supervisor topology. The driver launches separate workload and supervisor containers, provisions a private authenticated channel, and denies direct workload egress.

Related Issue

Part of #1737.

Changes

• Implement the shared isolation contract in the existing Podman driver crate.
• Provision the sandbox runtime, supervisor channel, bootstrap material, and lifecycle wiring.
• Mount a workload-owned 64 MiB tmpfs at /run for runtime state.
• Rotate generation, session token, and TLS identity before every restart.
• Bound image metadata inspection and reject dangling container roots.
• Add Podman lifecycle, identity, and gateway-start coverage.

Testing

• mise run pre-commit passes
• Podman unit tests pass (221 tests)
• Podman E2E validation delegated to remote CI

Checklist

• Follows Conventional Commits
• Authored commits are signed off (DCO)

Review remediation

• Add a workload-owned 64 MiB /run tmpfs and rotate generation, token, TLS identity, bootstrap, and supervisor channel material before restart.

Stack

1. feat(isolation): define the RFC 0012 boundary contract #2941 — contract
2. feat(isolation): add boundary protocol and Linux primitives #2942 — shared interface and primitives
3. feat(isolation): split supervisor and sandbox runtimes #3151 — supervisor and sandbox runtimes
4. feat(vm): run the supervisor outside the guest workload #2945 — VM driver
5. feat(docker): isolate workloads behind the host supervisor #2965 — Docker driver
6. feat(kubernetes): add proxy-pod isolation topology #3144 — Kubernetes proxy-pod topology
7. feat(podman): isolate workloads behind the host supervisor #3230 — Podman driver (this PR)
8. perf(isolation): add TCP and DNS benchmark harnesses #3229 — performance harnesses

[github-actions]

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[github-actions]

Label test:e2e applied for 355a410. Open the existing run and click Re-run all jobs to execute with the label set. The run will execute the standard E2E suite after building the required gateway and supervisor images once. The matching required CI gate status on this PR will flip green automatically once the run finishes.