feat(session): persist model tier overrides per session

Store per-session config in SQLite and route /model and /reset through command fast-paths so channel sessions keep independent model selection across reconnects and restarts.

src/memory/index.ts

@@ -8,3 +8,6 @@ export { VectorStore, cosineSimilarity, contentHash } from './vector-store.js';
 export type { VectorSearchResult, EmbeddingRow } from './vector-store.js';
 export { HybridSearch } from './hybrid-search.js';
 export type { HybridSearchResult } from './hybrid-search.js';
+export * from './categories.js';
+export { buildAdaptiveMemoryContext, buildRecentMemoryContext } from './adaptive.js';
+export type { AdaptiveMemoryConfig } from './adaptive.js';