Add npx-based installation support #144

Job	Run time
Validate plugin manifests	11s
Discover skills	10s
Validate skill (magpie-kernel-evaluator)	6s
Validate skill (tracelens-analysis-orchestrator)	8s
Validate skill (local-ai-use)	9s
Validate skill (serving-llms-on-instinct)	5s
Validate skill (local-ai-app-integration)	10s
Validate skills and plugin manifests	4s
	1m 3s

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