fix(plugins): narrow optional tool cold loads

extensions/diffs/openclaw.plugin.json

@@ -8,6 +8,11 @@
   "contracts": {
     "tools": ["diffs"]
   },
+  "toolMetadata": {
+    "diffs": {
+      "optional": true
+    }
+  },
   "skills": ["./skills"],
   "uiHints": {
     "viewerBaseUrl": {

extensions/llm-task/openclaw.plugin.json

@@ -8,6 +8,11 @@
   "contracts": {
     "tools": ["llm-task"]
   },
+  "toolMetadata": {
+    "llm-task": {
+      "optional": true
+    }
+  },
   "configSchema": {
     "type": "object",
     "additionalProperties": false,

extensions/lobster/openclaw.plugin.json

@@ -8,6 +8,11 @@
   "contracts": {
     "tools": ["lobster"]
   },
+  "toolMetadata": {
+    "lobster": {
+      "optional": true
+    }
+  },
   "configSchema": {
     "type": "object",
     "additionalProperties": false,