🤖 fix: report correct exit codes for signal-terminated background processes

When a background process is killed by signal (SIGTERM, SIGKILL, etc.),
Node's exit event provides code=null and signal name. The spawnBackground
handler was defaulting null to 0, making killed processes appear as
successful exits.

- Add getExitCode() helper to convert signals to Unix-conventional exit
  codes (128 + signal_number): SIGTERM=143, SIGKILL=137, etc.
- Add test verifying terminated processes report exit code >= 128

This restores behavior that was lost when bashExecutionService.ts was
removed during the Runtime refactor.

Author: ethanndickson

src/node/runtime/LocalRuntime.ts

@@ -35,6 +35,27 @@ import { getProjectName } from "@/node/utils/runtime/helpers";
 import { getErrorMessage } from "@/common/utils/errors";
 import { once } from "node:events";
 import { log } from "@/node/services/log";
+
+/**
+ * Convert Node.js exit event args to a single exit code.
+ * When a process is killed by signal, Node provides code=null and signal name.
+ * This converts to Unix-conventional exit codes (128 + signal_number).
+ */
+function getExitCode(code: number | null, signal: NodeJS.Signals | null): number {
+  if (code !== null) return code;
+  if (signal) {
+    const signalNumbers: Record<string, number> = {
+      SIGHUP: 1,
+      SIGINT: 2,
+      SIGQUIT: 3,
+      SIGKILL: 9,
+      SIGTERM: 15,
+    };
+    return 128 + (signalNumbers[signal] ?? 0);
+  }
+  return 0;
+}
+
 import { expandTilde } from "./tildeExpansion";
 
 /**
@@ -246,11 +267,11 @@ export class LocalRuntime implements Runtime {
       }
     });
 
-    childProcess.on("exit", (code) => {
+    childProcess.on("exit", (code, signal) => {
       // Flush remaining partial lines
       if (stdoutBuffer) handle._emitStdout(stdoutBuffer);
       if (stderrBuffer) handle._emitStderr(stderrBuffer);
-      handle._emitExit(code ?? 0);
+      handle._emitExit(getExitCode(code, signal));
     });
 
     handle = new LocalBackgroundHandle(disposable);

src/node/services/backgroundProcessManager.test.ts

@@ -224,5 +224,26 @@ describe("BackgroundProcessManager", () => {
         expect(proc?.status).toBe("killed");
       }
     });
+
+    it("should report non-zero exit code for signal-terminated processes", async () => {
+      // Spawn a long-running process
+      const result = await manager.spawn(runtime, testWorkspaceId, "sleep 60", {
+        cwd: process.cwd(),
+      });
+
+      if (result.success) {
+        // Terminate it (sends SIGTERM, then SIGKILL after 2s)
+        await manager.terminate(result.processId);
+
+        // Wait for exit to be recorded
+        await new Promise((resolve) => setTimeout(resolve, 100));
+
+        const proc = manager.getProcess(result.processId);
+        expect(proc).not.toBeNull();
+        // Exit code should be 128 + signal number (SIGTERM=15 → 143, SIGKILL=9 → 137)
+        // Either is acceptable depending on timing
+        expect(proc!.exitCode).toBeGreaterThanOrEqual(128);
+      }
+    });
   });
 });