feat(config): support PORT env override

docs/plans/state.json

@@ -43,6 +43,18 @@
       "test_status": "pnpm test:run + pnpm typecheck passing"
     },
 
+    "deployment-port-env-override": {
+      "status": "completed",
+      "date": "2026-02-16",
+      "updated": "2026-02-16",
+      "summary": "Added PORT environment variable override support so PaaS deployments can bind the gateway to the platform-assigned port without requiring config changes.",
+      "files_modified": [
+        "src/config/loader.ts",
+        "src/config/loader.test.ts"
+      ],
+      "test_status": "pnpm test:run + pnpm typecheck passing"
+    },
+
     "openclaw-gap-roadmap": {
       "file": "2026-02-15-openclaw-gap-roadmap.md",
       "status": "planned",
@@ -2132,7 +2144,7 @@
   },
 
   "overall_progress": {
-    "total_test_count": 1692,
+    "total_test_count": 1694,
     "all_tests_passing": true,
     "p0_completion": "3/3 (100%)",
     "p1_completion": "4/4 (100%)",