chore: add copilot style guide #239

Job	Run time
Detect Changes	8s
sanitize-branch-name	3s
Build and Test Services (document-extractor)	2m 7s
Build and Test Services (mcp-server)	59s
Build and Test Services (admin-backend)	1m 7s
Build and Test Services (rag-backend)	1m 20s
Build and Test Libraries	0s
Validate Infrastructure	0s
Build and Test Frontend	0s
CI Summary	2s
	5m 46s

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