P3: add mesh networking and pod IP routing

[chimerakang]

Summary

• add Kubernetes-coordinated Pod IPAM with restart recovery
• add WireGuard mesh configuration, key management, route reconciliation, MTU handling, and IPv6 route-family support
• add host Pod network path wiring, Pod IP/HostIP readiness reporting, and kubectl port-forward support
• document P3 networking setup and update the example config

Review fixes included

• serialize concurrent CreatePod calls so duplicate VK retries cannot leak extra runtime workloads
• apply configured WireGuard MTU during interface setup
• choose macOS route family from CIDR so IPv6 routes use -inet6

Validation

• go test ./...
• go vet ./...
• make build

Closes #20
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Closes #24