feat(connectivity): the bundled mcp-kubernetes registers as a family member (cluster + family) or not at all — a single-installation deployment gets the same x_kubernetes_* family UX as the fleet

[teemow]

Problem

helm/agent-platform-connectivity/templates/mcp-kubernetes/mcpserver.yaml renders the MCPServer mcp-kubernetes whenever components.mcp-kubernetes and components.muster are on: a family-less singleton (x_mcp-kubernetes_<tool>, no management_cluster argument) labelled agent-platform.giantswarm.io/tool-group: infrastructure. Installations do not use it — their mcp-kubernetes is a separate release, registered by agent-platform-mcps as <cluster>-mcp-kubernetes with spec.family {name: kubernetes, instanceArg: management_cluster} and the muster.giantswarm.io/management-cluster label — so a deployment that runs the bundled component (the local lab today; any single-installation deployment) gets a different tool namespace than the fleet, and one that wants the family shape ends up with two registrations of the same server (the singleton plus an mcps entry), i.e. duplicate tools.

Decision behind this (2026-09-12): the infrastructure servers are families only, everywhere. The lab side is giantswarm/agentlab#168.

Proposed solution

Give the bundled registration the two shapes an installation can want, and nothing else:

• mcp-kubernetes.mcpServer.enabled (default true): render the CR or leave the registration to agent-platform-mcps.
• mcp-kubernetes.mcpServer.family ({name: kubernetes, instanceArg: management_cluster}, off by default for compatibility) together with mcp-kubernetes.mcpServer.managementCluster (the value the management_cluster argument selects; defaults to the installation's name): when set, the CR carries spec.family, the muster.giantswarm.io/management-cluster label and is named <managementCluster>-mcp-kubernetes, exactly as agent-platform-mcps renders a member.

Alternatively the bundled registration is routed through the chart's agent-platform-mcps.mcpServers list (one rendering path for every infrastructure server). Either way the family block and the tool-group label follow agent-platform-mcps' conventions (muster.families.<group>.toolGroup).

Acceptance criteria

• The three shapes render (singleton as today; family member; not rendered) and the values schema and README describe them
• Renaming to <cluster>-mcp-kubernetes with the family block does not break platform-test-style callers that opt in (The lab registers its own cluster as the infrastructure families (kubernetes, prometheus; capi with #56) the way an installation does — the Infrastructure preset resolves to x_kubernetes_*/x_prometheus_* with management_cluster=agentlab, and the fake fleet retires agentlab#168 tracks the lab side)
• The ATS smoke and make verify are unaffected by the default
• The default stays the singleton until the lab and the docs have moved (a later major flips it)