chore(gates): zero clippy warnings and a buildable sandbox example on Windows

The full-workspace gates had never run on this platform: collapsible
ifs in the Windows shell probe, a same-type cast in the crash handler,
an unused AsRawHandle import, and the sandbox smoke-test example
building its unix-only body (libc, kernel enforcement) unconditionally.
The example now stubs main off-unix; formatting reflow from cargo fmt.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KSy9S31pZNWXtRZNVJ1sDf

crates/codegen/kigi-sampling-types/src/error.rs

@@ -388,7 +388,9 @@ mod tests {
 
     #[test]
     fn retryable_api_status_covers_edge_5xx_and_excludes_broken_tls() {
-        for status in [429u16, 500, 502, 503, 504, 520, 521, 522, 523, 524, 529, 530, 599] {
+        for status in [
+            429u16, 500, 502, 503, 504, 520, 521, 522, 523, 524, 529, 530, 599,
+        ] {
             assert!(is_retryable_api_status(status), "should retry {status}");
         }
         // Cloudflare 525/526: origin TLS handshake / invalid certificate —