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/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "control-plane"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+authors.workspace = true
+
+[dependencies]
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+rusqlite = { version = "0.34", features = ["bundled"] }
+uuid = { version = "1", features = ["v4"] }
+chrono = { version = "0.4", features = ["serde"] }
+tracing = "0.1"
+sha2 = "0.10"
+hex = "0.4"
+
+[dev-dependencies]
+tempfile = "3"