Tokuno scribes currently load only `SBScribe`, so the existing Zento scribe does not offer the Book of Bushido or Book of Ninjitsu. Add the existing `SBSamurai` and `SBNinja` inventories when `Core.SE && IsTokunoVendor`.
This reuses the existing book prices and default stock quantities. It does not change NPC placement, trainer behavior, or inventories outside Tokuno.
### Sources and reasoning
- The [official UO Ninjitsu guide](https://uo.com/wiki/ultima-online-wiki/skills/ninjitsu/) identifies the scribe at Rokuon Cultural Center in Zento as a seller of the Book of Ninjitsu.
- [UOGuide: Bushido](https://www.uoguide.com/Bushido), documenting standard UO, explicitly lists Tokuno Islands scribe NPCs as a source for the Book of Bushido. This supports adding both book inventories to Tokuno scribes.
- Documentation distinction: the [official UO Bushido guide](https://uo.com/wiki/ultima-online-wiki/skills/bushido/) describes the Zento seller as a samurai trainer, rather than a scribe. The Bushido scribe change follows the explicit UOGuide description. These references do not independently establish the exact historical introduction date or original prices.
### Validation
- Built the change in a customized ModernUO 0.15.6.145 deployment: Release, linux-x64, zero warnings or errors.
- In-game with Mondain's Legacy enabled: both books appeared on the existing Zento scribe, and a player successfully purchased both.
- Reviewed the expansion/location guard for pre-SE and non-Tokuno behavior; those cases were not gameplay-tested. This exact patch has not been built against current upstream main.
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