refactor: move programs into programs and UIs into apps

This refactors the repository structure as it has grown over time.

programs/stablecoin/methods/src/lib.rs

@@ -0,0 +1,12 @@
+//! Host-side embedding of the stablecoin RISC Zero guest ELF.
+//!
+//! Re-exports the constants produced by `build.rs` via `risc0_build::embed_methods` —
+//! `STABLECOIN_ELF`, `STABLECOIN_PATH`, and `STABLECOIN_ID` — used by host code to
+//! load and identify the guest binary.
+
+#![allow(
+    missing_docs,
+    reason = "constants below are generated by risc0_build::embed_methods at build time"
+)]
+
+include!(concat!(env!("OUT_DIR"), "/methods.rs"));