chore: align sqlite control plane architecture

- replace default Convex control-plane wording with Rust SQLite control-plane across architecture, AGENTS, Reasonix, and design docs

- retire root Convex functions source and deploy script into recycle while keeping explicit cloud/compat/sync-replica boundaries

- add control-plane migration guard/docs and keep CodeGraph refreshed after the SQLite control-plane cutover

rust/crates/control-plane/src/lib.rs

@@ -0,0 +1,11 @@
+pub mod error;
+pub mod migrations;
+pub mod model;
+pub mod sqlite;
+pub mod store;
+
+pub use error::ControlPlaneError;
+pub use migrations::run_migrations;
+pub use model::*;
+pub use sqlite::SqliteControlPlaneStore;
+pub use store::*;