Add npx-based installation support #145

Job	Run time
Validate plugin manifests	10s
Discover skills	7s
Validate skill (magpie-kernel-evaluator)	9s
Validate skill (local-ai-app-integration)	7s
Validate skill (tracelens-analysis-orchestrator)	9s
Validate skill (serving-llms-on-instinct)	6s
Validate skill (local-ai-use)	6s
Validate skills and plugin manifests	4s
	58s

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