fix(plugins): 内置清单终审 15 → 13 —— kbtree/multimodal 翻案加回

## 翻案依据（逐方法对照公开 SDK，非方法名 grep）

初判把 kbtree/multimodal 归入"只用公开 SDK"，错了。两边的
s.Knowledge() / s.LLM() **同名但接口面不同**：

- kbtree 需要 KnowledgeAPI.Subtree/CategoryCounts/SearchIn/Categories
  与 KnowledgeTreeView/KnowledgeCategoryCount 类型 —— 公开 KnowledgeAPI
  只有 Search/Add/List，树视图类型公开面根本没有
- multimodal 需要 LLMAPI.Chat + LLMMessage/LLMContentBlock ——
  公开 LLMAPI 只有 ListSources/SetSource/CurrentSource，没有 Chat

外置它们 = OCR/看图/转写、知识树浏览静默失效。

## 最终内置 13 个

  cli webui agentcli healthcheck pluginmgr seq remotedevice
  clawhubadapter kbtree multimodal cfgmgr skillmgr seemedia

外置 5 个（SDK 仓 example/ 已提供工程并已部署验证）：
  cmd localuse mcp（本轮）+ ai_image files（此前）+ timer（更早）

## 文档同步（中英 6 份）

数量 11 → 13；判定标准小节补「终审翻案」与教训：
**判外置与否必须逐方法对照公开接口，同名方法不等于同面。**

验证：go build/vet/test 全绿；生产实例已部署新内核 + 新插件包，
四个按需插件经 plugin_start 拉起、工具全部注册（cmd_run /
local_screensee / mcp_* / files_edit_line 实核）。

README_EN.md

@@ -216,7 +216,7 @@ internal/
 ├── memory/         Three-layer memory: Graph(SQLite) / Document(JSON+TF-IDF) / Text(JSONL) + StaticEmbedder(pretrained word embedding/TF-IDF fallback) + CleanTemplateText(de-template)
 ├── knowledge/      Knowledge base (filesystem + TF-IDF)
 ├── plugin/         Plugin registry + subprocess loader (stdio RPC + shared memory segment + event ring)
-├── plugins/        11 built-in plugins (webui/cli/agentcli/cfgmgr/healthcheck/pluginmgr/clawhubadapter/remotedevice/skillmgr/seemedia/seq) — see ARCHITECTURE "which plugins stay built-in"
+├── plugins/        13 built-in plugins (webui/cli/agentcli/cfgmgr/healthcheck/kbtree/multimodal/pluginmgr/clawhubadapter/remotedevice/skillmgr/seemedia/seq) — see ARCHITECTURE "Which Plugins Stay Built-in"
 ├── sdk/            PluginSDK (Tool/Stage/Event three channels)
 ├── config/         SQLite config center
 ├── events/         Event bus
@@ -416,7 +416,7 @@ private included), with no same-license obligation and no §13 network clause. T
 vitality of the third-party plugin ecosystem rest on this.
 
 The boundary is clean: **AGPL covers the kernel and the bundled plugins** (`homed`, `internal/`,
-the 11 built-in plugins under `internal/plugins/`); **MIT covers the public SDK** (`sdk/`, whose
+the 13 built-in plugins under `internal/plugins/`); **MIT covers the public SDK** (`sdk/`, whose
 `go.mod` has zero external dependencies and imports only the Go standard library — it never
 references any kernel code). Process isolation is beside the point here — what decides the
 license is the linked SDK code itself, and that code is MIT.