feat(plugin): add WhisperGate rule engine and model override hook

plugin/openclaw.plugin.json

@@ -0,0 +1,20 @@
+{
+  "id": "whispergate",
+  "name": "WhisperGate",
+  "version": "0.1.0",
+  "description": "Rule-based no-reply gate with provider/model override",
+  "entry": "./index.ts",
+  "configSchema": {
+    "type": "object",
+    "additionalProperties": false,
+    "properties": {
+      "enabled": { "type": "boolean", "default": true },
+      "discordOnly": { "type": "boolean", "default": true },
+      "bypassUserIds": { "type": "array", "items": { "type": "string" }, "default": [] },
+      "endSymbols": { "type": "array", "items": { "type": "string" }, "default": ["。", "！", "？", ".", "!", "?"] },
+      "noReplyProvider": { "type": "string" },
+      "noReplyModel": { "type": "string" }
+    },
+    "required": ["noReplyProvider", "noReplyModel"]
+  }
+}