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-shell/src/test_support/lsp_runtime.rs

@@ -33,8 +33,7 @@ pub(crate) fn ctx_with_toggle(toggle: HashMap<String, bool>) -> SubagentSpawnCon
     let (tx, _rx) = mpsc::unbounded_channel();
     SubagentSpawnContext {
         lsp: None,
-        spawn_limits:
-            kigi_tools::implementations::kigi::task::admission::SubagentLimits::default(),
+        spawn_limits: kigi_tools::implementations::kigi::task::admission::SubagentLimits::default(),
         spawn_permits: std::sync::Arc::new(tokio::sync::Semaphore::new(
             kigi_tools::implementations::kigi::task::admission::SubagentLimits::default()
                 .effective_max_concurrent(),