docs: add public unbounded-net VNet peering lab

[bcho]

Summary

• Add a new lab for public AKS + cross-region VNet peering + unbounded-net CNI
• Document no-gateway-pool private-L3 SitePeering flow
• Update labs index and topic matrix

Validation

• Deployed a real AKS public no-CNI cluster and cross-region Flex VM
• Installed unbounded-net and joined the Flex node
• Verified node-to-node traffic, Flex exec/logs, and cross-site pod-to-pod ping

Validation environment:

• AKS: aks-pubpeer06292201 in eastus2
• Flex VM/node: flex-pubpeer06292201 in southcentralus
• AKS pod -> Flex pod ping: 0% packet loss
• Flex pod -> AKS pod ping: 0% packet loss

[Copilot]

Pull request overview

Adds a new end-to-end lab documenting a public AKS cluster with --network-plugin none, unbounded-net CNI, and a cross-region Flex VM connected via global VNet peering (private-L3 SitePeering), and updates existing setup docs to use safer file installation commands while standardizing on a 022 umask for bootstrap.

Changes:

• Add a new lab: public AKS + cross-region VNet peering + unbounded-net + Flex node join/validation workflow.
• Update labs index/topic matrix to include the new lab and cross-reference related topics.
• Standardize config placement instructions (use install, keep config 0600, set umask 022 before bootstrap) across README and existing labs/usages docs.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
README.md	Switch config install to install and document umask 022 before bootstrap.
docs/usages/aks-flex-config.md	Align usage doc with install + umask 022 bootstrap guidance.
docs/labs/README.md	Add new lab link and update topic matrix cross-references.
docs/labs/gpu-node-setup.md	Align GPU lab config install + umask 022 guidance.
docs/labs/aks-public-cluster-unbounded-net-wireguard.md	Align WireGuard lab config install + umask 022 guidance.
docs/labs/aks-public-cluster-unbounded-net-vnet-peering.md	New lab for public AKS + VNet peering + unbounded-net + Flex node validation.
docs/labs/aks-private-cluster-unbounded-net.md	Align private unbounded lab config install + umask 022 guidance.
docs/labs/aks-private-cluster-cilium.md	Align private cilium lab config install + umask 022 guidance.

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