feat(provider/lambdai): Kubernetes node-data-broker support

[alaski-lambda]

Description

Add lambdai.GetNodeAnnotations, which derives Topograph's instance and region node annotations from a node's .spec.providerID (lambda://) and its topology.kubernetes.io/region label, and dispatch to it from the node-data-broker so the k8s engine can discover and label Lambda nodes. Register lambdai in the provider overview and docs nav.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.
• All commits are signed off per DCO (git commit -s).

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[greptile-apps]

Greptile Summary

This PR adds Kubernetes node-data-broker support for the Lambda AI provider by implementing GetNodeAnnotations in pkg/providers/lambdai/k8s.go, wiring it into the broker's provider switch, and registering Lambda in the docs nav and overview.

• GetNodeAnnotations derives the Topograph instance annotation from spec.providerID (lambda://<id>) and the region annotation from the topology.kubernetes.io/region label, with correct error-on-empty behavior so the init container retries until the lambda-cloud-controller has initialized the node.
• The docs entries in docs/index.yml and docs/overview.md reference providers/lambdai.md, but that file is not present in the repository — every other provider in the nav has a corresponding doc file, so this will produce a broken link on the docs site.

Confidence Score: 4/5

The core Go implementation is solid and the broker wiring is correct, but the docs nav and overview reference a provider page that does not yet exist.

The new GetNodeAnnotations function, its tests, and the broker switch entry are all correct. The only gap is that docs/providers/lambdai.md is referenced in both docs/index.yml and docs/overview.md but is absent from the repository, which will produce broken links on the docs site.

docs/index.yml and docs/overview.md reference providers/lambdai.md, which does not exist.

Important Files Changed

Filename	Overview
pkg/providers/lambdai/k8s.go	New GetNodeAnnotations function; extracts instance ID from spec.providerID and region from topology label. Logic is correct, nil-map access is safe in Go, and error paths retry correctly in the init container.
pkg/providers/lambdai/k8s_test.go	Five table-driven test cases covering success, node-not-found, missing prefix, empty providerID, and missing region label — good coverage.
cmd/node-data-broker/main.go	Adds lambdai.NAME case to the provider switch and imports the lambdai package; wiring is correct.
docs/index.yml	Adds Lambda nav entry pointing to providers/lambdai.md, which does not exist in the repository — broken link.
docs/overview.md	Adds Lambda to the supported providers list and the scenario table; links to the non-existent providers/lambdai.md.
charts/topograph/values.yaml	Comment updated to include lambdai as a valid provider name value — straightforward documentation fix.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant NDB as node-data-broker (init container)
    participant K8s as Kubernetes API
    participant Lambda as lambda-cloud-controller

    Lambda->>K8s: "Sets Node.spec.providerID = "lambda://<id>""
    Lambda->>K8s: Sets Node label topology.kubernetes.io/region

    NDB->>K8s: GET Node (lambdai.GetNodeAnnotations)
    alt providerID or region label missing
        K8s-->>NDB: Node missing fields
        NDB-->>NDB: Return error - init container retries
    else fields present
        K8s-->>NDB: Node with providerID + region label
        NDB->>NDB: Extract instance ID via strings.CutPrefix
        NDB->>K8s: GET Node (broker.apply)
        NDB->>K8s: PATCH Node annotations (topograph.nvidia.com/instance, topograph.nvidia.com/region)
    end

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%%{init: {'theme': 'base', 'themeVariables': {"darkMode": true, "background": "#0d1117", "primaryColor": "#21262d", "primaryTextColor": "#e6edf3", "primaryBorderColor": "#8b949e", "lineColor": "#8b949e", "textColor": "#e6edf3", "edgeLabelBackground": "#161b22", "actorBkg": "#21262d", "actorBorder": "#8b949e", "actorTextColor": "#e6edf3", "actorLineColor": "#8b949e", "signalColor": "#8b949e", "signalTextColor": "#e6edf3", "noteBkgColor": "#373320", "noteBorderColor": "#d4a72c", "noteTextColor": "#f0e6c0", "labelBoxBkgColor": "#21262d", "labelBoxBorderColor": "#8b949e", "labelTextColor": "#e6edf3", "loopTextColor": "#e6edf3", "activationBkgColor": "#30363d", "activationBorderColor": "#8b949e"}}}%%
sequenceDiagram
    participant NDB as node-data-broker (init container)
    participant K8s as Kubernetes API
    participant Lambda as lambda-cloud-controller

    Lambda->>K8s: "Sets Node.spec.providerID = "lambda://<id>""
    Lambda->>K8s: Sets Node label topology.kubernetes.io/region

    NDB->>K8s: GET Node (lambdai.GetNodeAnnotations)
    alt providerID or region label missing
        K8s-->>NDB: Node missing fields
        NDB-->>NDB: Return error - init container retries
    else fields present
        K8s-->>NDB: Node with providerID + region label
        NDB->>NDB: Extract instance ID via strings.CutPrefix
        NDB->>K8s: GET Node (broker.apply)
        NDB->>K8s: PATCH Node annotations (topograph.nvidia.com/instance, topograph.nvidia.com/region)
    end

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[greptile-apps]

Missing documentation file — broken nav link

docs/index.yml and docs/overview.md both reference providers/lambdai.md, but the file docs/providers/lambdai.md does not exist in the repository. Every other provider entry in the nav (aws, gcp, oci, nebius, nscale, infiniband, netq, dra) has a corresponding file under docs/providers/. Clicking the "Lambda" nav entry will result in a 404 on the docs site. A provider page is needed before this navigation entry can be wired up.