docs: add AgentsKit TypeScript RAG example

[EmersonBraun]

Summary

• add a provider-neutral TypeScript RAG example using @agentskit/rag and Qdrant-backed @agentskit/memory
• include a deterministic local embedder so the full flow runs without credentials
• create the collection, ingest chunked documents, preserve source IDs, and retrieve ranked context
• add strict TypeScript and credential-free embedder tests
• add one README index row

Validation

• installed the published @agentskit/memory@0.11.4 with npm — 0 vulnerabilities
• npm test — 2 passed
• npm run check
• live Qdrant 1.15.4 ingest and retrieval returned the expected AgentsKit document first with score 0.6495
• git diff --check