feat(rust): update project description to better reflect AI focus

- Change description from "Hierarchical, reasoning-native document
  intelligence engine" to "Reasoning-native document intelligence
  engine for AI"
- Removes hierarchical aspect and adds clearer AI context

Author: zTgx

rust/Cargo.toml

@@ -3,7 +3,7 @@ name = "vectorless"
 version.workspace = true
 edition.workspace = true
 authors.workspace = true
-description = "Hierarchical, reasoning-native document intelligence engine"
+description = "Reasoning-native document intelligence engine for AI"
 license.workspace = true
 repository.workspace = true
 homepage.workspace = true