fix(kubernetes): scope resource admission RBAC

[drew]

Summary

Follow up on #3538 by limiting Kubernetes resource-admission reads to caller-selectable resources. Default installations receive no PVC, Secret, or ConfigMap read permission. PVC metadata reads are granted only when caller driver config is explicitly enabled.

Related Issue

No issue required: this is a localized least-privilege correction to #3538.

Changes

• remove Secret and ConfigMap metadata reads from Kubernetes resource admission
• treat configured image-pull Secrets as operator-selected infrastructure rather than caller attachments
• retain managed-mode image-pull Secret copying with existing name-restricted reads and gateway ownership checks
• reject unsupported Secret/ConfigMap volumes and environment references without expanding RBAC
• omit PVC reads by default and render them only with server.drivers.kubernetes.allowDriverConfig=true
• add the matching gateway.allowDriverConfig opt-in to split workspace releases
• update operator documentation, architecture notes, and deployment/debugging skills
• add Helm and driver regression coverage for the narrowed permissions

Testing

• mise run pre-commit passes
• cargo test -p openshell-driver-kubernetes --lib passes (256 tests)
• mise run helm:test passes (171 tests)
• E2E tests added/updated (not required; no runtime infrastructure path changed)

Checklist

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

[github-actions]

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