Series indicator development

File structure

All files live in src/{category}/{Indicator}/:

File	Purpose
`{Indicator}.StaticSeries.cs`	Static partial class — `To{Indicator}()` + `To{Indicator}List()` entry points
`{Indicator}.StreamHub.cs`	Hub class (internal ctor) + `To{Indicator}Hub()` extension
`{Indicator}.BufferList.cs`	List class + `To{Indicator}List()` extension
`{Indicator}.Catalog.cs`	`CommonListing`, `SeriesListing`, `StreamListing`, `BufferListing`
`{Indicator}.Models.cs`	Result record(s)
`{Indicator}.Utilities.cs`	`Validate()` (internal), `Increment()` (public), `RemoveWarmupPeriods()`
`I{Indicator}.cs`	Parameter interface (parameter properties only; NOT result properties)

Test files mirror in tests/indicators/{category}/{Indicator}/: