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-config/src/shell.rs

@@ -78,11 +78,10 @@ pub fn detect_windows_shell() -> &'static WindowsShell {
             kigi_tty_utils::detach_std_command(&mut cmd);
             cmd.arg("pwsh.exe").stdin(std::process::Stdio::null());
             cmd.output()
-        } {
-            if output.status.success() {
-                tracing::info!("Windows shell: pwsh");
-                return WindowsShell::Pwsh;
-            }
+        } && output.status.success()
+        {
+            tracing::info!("Windows shell: pwsh");
+            return WindowsShell::Pwsh;
         }
 
         // powershell.exe (Windows PowerShell 5.1).
@@ -131,14 +130,13 @@ fn find_git_bash() -> Option<String> {
         kigi_tty_utils::detach_std_command(&mut cmd);
         cmd.arg("bash.exe").stdin(std::process::Stdio::null());
         cmd.output()
-    } {
-        if output.status.success() {
-            let stdout = String::from_utf8_lossy(&output.stdout);
-            for line in stdout.lines() {
-                let line = line.trim();
-                if line.to_ascii_lowercase().contains("git") {
-                    return Some(line.to_string());
-                }
+    } && output.status.success()
+    {
+        let stdout = String::from_utf8_lossy(&output.stdout);
+        for line in stdout.lines() {
+            let line = line.trim();
+            if line.to_ascii_lowercase().contains("git") {
+                return Some(line.to_string());
             }
         }
     }