fix: graceful process shutdown in macOS app

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/EXO/EXO/ExoProcessController.swift

@@ -118,11 +118,37 @@ final class ExoProcessController: ObservableObject {
             return
         }
         process.terminationHandler = nil
-        if process.isRunning {
-            process.terminate()
-        }
-        self.process = nil
         status = .stopped
+
+        guard process.isRunning else {
+            self.process = nil
+            return
+        }
+
+        let proc = process
+        self.process = nil
+
+        Task.detached {
+            proc.interrupt()
+
+            for _ in 0..<50 {
+                if !proc.isRunning { return }
+                try? await Task.sleep(nanoseconds: 100_000_000)
+            }
+
+            if proc.isRunning {
+                proc.terminate()
+            }
+
+            for _ in 0..<30 {
+                if !proc.isRunning { return }
+                try? await Task.sleep(nanoseconds: 100_000_000)
+            }
+
+            if proc.isRunning {
+                kill(proc.processIdentifier, SIGKILL)
+            }
+        }
     }
 
     func restart() {

src/exo/main.py

@@ -137,6 +137,7 @@ class Node:
     async def run(self):
         async with self._tg as tg:
             signal.signal(signal.SIGINT, lambda _, __: self.shutdown())
+            signal.signal(signal.SIGTERM, lambda _, __: self.shutdown())
             tg.start_soon(self.router.run)
             tg.start_soon(self.election.run)
             if self.download_coordinator: