[codex] update GraphQL node and lookup APIs

[juliuskrah]

Summary

• add Relay global ID handling for node lookups and ID-based resolver paths
• add cursor pagination updates for namespaces, categories, and collections
• replace duplicate GraphQL lookup fields with @OneOf selector inputs
• update namespace/auth docs, API examples, feature contracts, and admin GraphQL documents

Validation

• cd gitstore-api && go generate ./...
• cd gitstore-api && go test ./...
• cd gitstore-api && go vet ./...
• ./scripts/check-go-license-headers.sh --all

Notes

• This PR contains the six local commits that were ahead of origin/main.

[chatgpt-codex-connector]

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