test(sharding): G3 foundation 3 partial 마감 (ShardingMode/ShardsSpec/plugin) - #62

Summary

G3 sharding foundation 3 partial sub-task finalize — ShardingMode field + ShardsSpec topology + sharding plugin interface 모두 unit test 보강 + ROADMAP marker [~] → [x].

변경 내용

• api/v1alpha1/postgrescluster_types_test.go (신규): TestShardingMode (constants/round-trip/string cmp) + TestShardsSpec (field preservation + DeepCopy + Replicas=0 dev mode)
• internal/plugin/sharding/api_test.go (확장): TestRegistry_Register_Get / NotFound / Names
• ROADMAP.md G3 3 sub-task marker 갱신

v1.0 로드맵 매핑

~/.claude/plans/1-swift-anchor.md Rev 4 §Phase A #2
Gate G3 D.8.x 3 sub-task [~] → [x] (control plane finalize)

검증 명령

go test ./api/v1alpha1/... -run TestShardingMode -v
go test ./api/v1alpha1/... -run TestShardsSpec -v
go test ./internal/plugin/sharding/... -v

정책 정합

• Rebased onto origin/main 53dbdf0, WIP commit 72271d8 drop
• fallback: gh CLI graphql 0/0 → gh api POST REST direct