Stateless Memory hooks SentenceTransformer into SillyTavern

This is the right way to do ST memory: use embeddings for fuzzy recall, but keep the actual memory primitive in Lorebooks where users can inspect and prune it.

• –ST docs already describe World Info evaluation as stateless, so the project is aligning with the platform’s own memory model instead of fighting it. https://docs.sillytavern.app/usage/core-concepts/worldinfo/
• –SillyTavern Extras flags ChromaDB as part of the old Smart Context path, which is deprecated, so skipping a separate vector DB feels timely. https://github.com/SillyTavern/SillyTavern-Extras
• –SentenceTransformer similarity should beat keyword-only recall for fuzzy callbacks and character memory, but the quality bar will hinge on threshold tuning and how messy the Lorebook gets as chats grow.
• –The tradeoff is simplicity over scale: great for a self-hosted RP workflow, less compelling if you need a shared memory service across many chats or users.