fix(lifecycle): use ProcessLifecycle for coordinated shutdown

Replace per-Watcher SIGINT handlers with a single ProcessLifecycle.install()
in TsWatch.start(). This eliminates competing signal handler races that left
orphaned child processes. Add @push.rocks/smartexit as direct dependency.

package.json

@@ -31,11 +31,12 @@
     "@push.rocks/npmextra": "^5.3.3",
     "@push.rocks/smartcli": "^4.0.20",
     "@push.rocks/smartdelay": "^3.0.5",
+    "@push.rocks/smartexit": "2.0.0",
     "@push.rocks/smartfs": "^1.3.1",
     "@push.rocks/smartinteract": "^2.0.16",
     "@push.rocks/smartlog": "^3.1.10",
     "@push.rocks/smartlog-destination-local": "^9.0.2",
-    "@push.rocks/smartshell": "^3.3.2",
+    "@push.rocks/smartshell": "^3.3.3",
     "@push.rocks/smartwatch": "^6.3.0",
     "@push.rocks/taskbuffer": "^4.2.0"
   },