Exit desktop process immediately after window close

window.run() returning unwinds through main, which races a still-live
zbus/keyring background thread's TLS teardown and aborts with
"thread local ... during or after destruction". Skip that unwind with
a hard exit once the run succeeds; dr_ui::run itself is left alone
since the Android entry point also calls it and must not be exited.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/darkroom-desktop/src/main.rs

@@ -17,5 +17,12 @@ fn main() -> anyhow::Result<()> {
         eprintln!("usage: darkroom-desktop <file-or-directory>...");
     }
 
-    dr_ui::run(paths)
+    dr_ui::run(paths)?;
+
+    // Skip Rust's normal static/thread-local teardown on the way out: a
+    // background zbus/keyring connection opened by dr_ui::launch_ui can
+    // still be alive here, and unwinding through it races its async-io
+    // reactor thread, panicking with "thread local ... during or after
+    // destruction" when the window is closed.
+    std::process::exit(0);
 }