refactor(mir): phase260 p0 edge-args plumbing (strangler) + ssot api + docs

src/mir/builder/control_flow/joinir/api/mod.rs

@@ -0,0 +1,14 @@
+//! JoinIR integration API (SSOT entry points)
+//!
+//! Purpose: provide a small, stable surface for pattern lowerers and merge code.
+//! This reduces "where should I call this from?" drift and avoids re-implementing
+//! contract logic (SSOT, fail-fast checks) in each pattern.
+//!
+//! Policy:
+//! - Prefer SSOT helpers over ad-hoc logic in patterns.
+//! - Avoid guessing (order/layout/name) in callers; callers pass explicit intent.
+//! - Keep this module thin: mostly wrappers/re-exports with clear naming.
+
+pub(in crate::mir::builder) mod entry;
+pub(in crate::mir::builder) mod pipeline_contracts;
+pub(in crate::mir::builder) mod receiver;