Class HybridTrackSource

Aggregates optional historical (past) and (live) sources for a single track. Either facet may be omitted:

• VOD / static content: supply only past
• Pure live: supply only live
• Hybrid (catch-up + live tail): supply both.

Priority handling note: publisher priority is defined on the Track metadata (see Track.publisherPriority). The library rounds non-integer values and clamps priority into [0,255] there; this interface simply expresses what content is available, independent of priority semantics.