Assemble P1-P4: advance module gitlinks (core 992d601, backend 97b90ad, frontend)

Details (original message):
Assemble P1-P4: advance module gitlinks (core 992d601, backend 97b90ad, frontend), cross-repo Makefile with contracts sync and single-binary build, example plugin assets, demo target.

plugins/example/cards/note.json

@@ -0,0 +1 @@
+{ "kind": "note", "data": [ { "type": "markdown", "markdown": "**插件卡片模板**（kind=note）——卡片类型同样走 UI schema 词汇。" } ] }

plugins/example/intents/demo.json

@@ -0,0 +1,3 @@
+[
+  { "id": "demo_intent", "domain": "demo", "description": "示例意图：命中『示例/演示』关键词", "includes_any": ["示例", "演示"], "slots": [] }
+]

plugins/example/panels/demo.json

@@ -0,0 +1,9 @@
+{
+  "id": "demo",
+  "title": "示例面板",
+  "body": [
+    { "type": "markdown", "markdown": "## 示例插件面板\n\n本面板由插件声明（UI schema），前端通用渲染器渲染——插件未注入任何 React 组件。" },
+    { "type": "kv", "title": "能力清单", "kv": [["工具", "http_echo（声明式 HTTP）"], ["意图", "demo_intent"], ["卡片", "note"], ["提示词", "assistant.md"]] },
+    { "type": "list", "title": "装卸语义", "items": ["目录移除插件后热重载即卸载", "内置工具不受影响（核心零回归）", "坏资产整批拒绝（fail-closed）"] }
+  ]
+}

plugins/example/plugin.json

@@ -0,0 +1,15 @@
+{
+  "id": "example",
+  "name": "示例插件",
+  "version": "0.1.0",
+  "apiVersion": "1.0",
+  "requires": { "network": ["api.example.com"] },
+  "provides": {
+    "tools": ["http_echo"],
+    "intents": ["demo"],
+    "panels": ["demo"],
+    "cards": ["note"],
+    "prompts": ["assistant"],
+    "settings": ["greeting"]
+  }
+}

plugins/example/prompts/assistant.md

@@ -0,0 +1 @@
+你是示例插件附带的助手画像模板。可复制为本用户画像后微调。

plugins/example/settings.json

@@ -0,0 +1,3 @@
+[
+  { "key": "greeting", "group": "plugin:example", "label": "问候语", "type": "string", "default": "你好", "effect": "hot" }
+]

plugins/example/tools/http_echo.json

@@ -0,0 +1,6 @@
+{
+  "name": "http_echo",
+  "description": "调用示例端点回显文本（声明式 HTTP 工具演示：修改 URL 指向你的服务即可复用）",
+  "parameters": { "type": "object", "properties": { "text": { "type": "string", "description": "要回显的文本" } }, "required": ["text"] },
+  "http": { "method": "POST", "url": "https://api.example.com/echo", "bodyTemplate": "{\"q\":\"{{param.text}}\"}", "resultPath": "echo", "timeoutMs": 10000 }
+}