refactor: rename crate fai-module-sdk -> chain-module-sdk

The SDK is product-scoped (Ch∆In's module SDK), not a generic vendor
crate — a future Brain SDK would collide. Crate + macros renamed to
chain-module-sdk[-macros]; repo + dir follow.

Signed-off-by: flemming-it <sf@flemming.it>

examples/echo/Cargo.toml

@@ -10,13 +10,13 @@ version = "0.1.0"
 edition = "2024"
 license = "Apache-2.0"
 publish = false
-description = "Reference module showing the minimum needed to write an F∆I module with fai-module-sdk."
+description = "Reference module showing the minimum needed to write an F∆I module with chain-module-sdk."
 
 [lib]
 crate-type = ["cdylib"]
 
 [dependencies]
-fai-module-sdk = { path = "../../crates/fai-module-sdk" }
+chain-module-sdk = { path = "../../crates/chain-module-sdk" }
 
 [profile.release]
 opt-level = "s"

examples/echo/src/lib.rs

@@ -5,7 +5,7 @@
 //! `unsafe_op_in_unsafe_fn` allow, no `export!` call, no manual
 //! Payload-variant matching.
 
-use fai_module_sdk::prelude::*;
+use chain_module_sdk::prelude::*;
 
 #[fai_module]
 fn invoke(_ctx: Context, inputs: Inputs) -> Result<Outputs, ModuleError> {