chore: import upstream snapshot with attribution

crates/jcode-build-support/examples/write_dev_sidecar.rs

@@ -0,0 +1,17 @@
+//! Write the dev-binary source metadata sidecar for the current repo state.
+//!
+//! Self-dev helper: after a direct `scripts/dev_cargo.sh build` (outside the
+//! coordinated build queue), the freshly built `target/selfdev/jcode` has no
+//! up-to-date `.source.json` sidecar, so `selfdev reload` refuses to publish
+//! it. Run this to stamp the binary with the *current* source state:
+//!
+//! ```sh
+//! cargo run -p jcode-build-support --example write_dev_sidecar
+//! ```
+fn main() -> anyhow::Result<()> {
+    let repo = std::env::current_dir()?;
+    let state = jcode_build_support::current_source_state(&repo)?;
+    let path = jcode_build_support::write_current_dev_binary_source_metadata(&repo, &state)?;
+    println!("wrote {} for {}", path.display(), state.version_label);
+    Ok(())
+}