chore: add clippy.toml with project lint configuration

clippy.toml

@@ -0,0 +1,12 @@
+# clippy.toml — project-wide Clippy configuration
+#
+# CI runs `cargo clippy --all-targets -- -D warnings`, so every lint here
+# must continue to pass under that invocation.  Add a comment for every
+# deliberate suppression so future contributors know what was decided and why.
+
+# `create_stream` is a public contract entry point whose eight parameters are
+# all distinct fields in the on-chain ABI.  Collapsing them into a struct
+# would only obscure the interface, so the too-many-arguments lint is raised
+# from the default threshold of 7 to 8 to accommodate that function without
+# needing an inline `#[allow]`.
+too-many-arguments-threshold = 8

contracts/stream/src/contract.rs

@@ -61,7 +61,8 @@ impl StreamContract {
     /// Only once all five pass are tokens transferred and the stream stored.
     // A contract entry point: every field is part of the public call shape,
     // so bundling them into a struct would only obscure the interface.
-    #[allow(clippy::too_many_arguments)]
+    // The too-many-arguments threshold is raised to 8 in clippy.toml to
+    // accommodate this function without an inline allow attribute.
     pub fn create_stream(
         env: Env,
         sender: Address,