Add Client interface with PutObject, GetObject, RemoveObject, PresignedGetObject, and
HandleError; Component now embeds Client with Native() as escape hatch for operations
not covered by the interface. Add xerrors dependency: HandleError maps minio-go error
codes to portable typed codes (NoSuchKey → ErrNotFound, AccessDenied →
ErrPermissionDenied, BucketAlreadyExists → ErrAlreadyExists, etc.). OnStop sets
c.mc = nil for lifecycle consistency. doc.go updated with launcher wiring, upload,
presigned URL, GetObject, and HandleError usage examples. API committed as stable.
What's included:
- Config with Endpoint, AccessKey, SecretKey, UseSSL, Bucket, Region (env-driven, embeddable)
- Transport field in Config for test injection (env:"-", nil uses minio-go default)
- Client interface: PutObject, GetObject, RemoveObject, PresignedGetObject, HandleError
- Component interface: launcher.Component + health.Checkable + Client + Native()
- New(logger, cfg) constructor for lifecycle registration via lc.Append
- Automatic bucket creation on OnStart if bucket does not exist
- Health check via BucketExists at LevelCritical priority
- HandleError: maps minio-go ErrorResponse codes to xerrors typed errors
- 21 unit tests using mock HTTP transport; no live server required
