feat: add tech-diagram skill (Mermaid 技术图生成) (#18)

## 概述 / Summary

新增市场技能 **tech-diagram**：把自然语言描述转成品牌一致的技术图（架构图/流程图/时序图/状态机/ER/类图/思维导图），在
DesireCore 对话内复用现有 Mermaid 渲染管线即时渲染为 SVG。

Adds a market skill **tech-diagram** that turns natural-language
descriptions into brand-consistent technical diagrams, rendered inline
as SVG by the existing Mermaid pipeline in the DesireCore chat.

灵感来源 / Inspired by
[fireworks-tech-graph](https://github.com/yizhiyanhua-ai/fireworks-tech-graph)
的三个设计思路：语义词汇表即数据、风格系统化、领域 Pattern 内置——并落到 DesireCore 自己的 3+2 设计令牌与领域模型上。

## 改动 / Changes

- `skills/tech-diagram/SKILL.md` + `SKILL.zh-CN.md`：双语技能正文（强制风格规则 +
语义词汇表 + 输出约定）
- `skills/tech-diagram/references/semantic-vocabulary.md`：概念→Mermaid
形状→3+2 classDef 完整映射
- `skills/tech-diagram/references/templates.md`：4 个 DesireCore
领域模板（Agent 架构 / Delegate 6 模式 / 三层记忆 / 关系图谱）+ 时序图示例
- `builtin-skills.json`：加入 `tech-diagram`
- `manifest.json`：`version` 1.2.1→1.2.2，`stats.totalSkills`
21→22，`lastUpdated`

## 设计要点 / Design

- **风格一致性**：每张图以 `%%{init}%%` 注入品牌主题（覆盖对话全局暗色），用 5 个 `classDef` 绑定
DesireCore 3+2 配色（green/blue/purple + warning orange / error red）。
- **语义优于视觉**：Agent→六边形、系统/记忆→圆角/圆柱、决策→菱形；箭头编码主数据流/记忆写入/异步/层级/上报。
- **领域内置**：直接对照 `delegate.ts` / `conversation-memory.ts` /
`relations/projector.ts` 给出可套用模板。

## 验证 / Verification

- ✅ `scripts/i18n/validate-i18n.py`：无 i18n 问题
- ✅ 用 app 同版本 **mermaid 11.15.0**（securityLevel: loose）解析 `templates.md`
全部 5 个图块，全部通过

skills/tech-diagram/references/templates.md

@@ -0,0 +1,119 @@
+# Built-in Templates (内置模板)
+
+Ready-to-use, brand-styled Mermaid for DesireCore's own architecture patterns.
+Adapt the labels to the user's subject; keep the header and `classDef`s intact.
+All four are verified to render.
+
+> Note: file paths like `lib/...` and `app/...` cited below refer to the
+> **DesireCore application codebase** where this skill runs at runtime — they do
+> not exist in this market repository.
+
+## 1. Agent architecture (Agent 架构图)
+
+Mirrors the delegate / skills / memory layout (`lib/agent-service/builtin-tools/delegate.ts`).
+
+```mermaid
+%%{init: {'theme':'base','themeVariables':{'primaryColor':'#F0F5FF','primaryBorderColor':'#007AFF','primaryTextColor':'#1d1d1f','lineColor':'#6e6e73','fontFamily':'-apple-system,SF Pro Text,Noto Sans SC,sans-serif'}}}%%
+flowchart TD
+    classDef agent  fill:#F6F3FF,stroke:#AF52DE,color:#1d1d1f
+    classDef system fill:#F0F5FF,stroke:#007AFF,color:#1d1d1f
+    classDef biz    fill:#F0FDF4,stroke:#34C759,color:#1d1d1f
+
+    U(["User"]):::biz
+    Core("DesireCore Core"):::system
+    A1{{"Legal Agent"}}:::agent
+    A2{{"Data Agent"}}:::agent
+    Skills["Skills / MCP Tools"]:::biz
+    Mem[("Conversation Memory")]:::system
+
+    U --> Core
+    Core --> A1
+    Core --> A2
+    A1 --> Skills
+    A2 --> Skills
+    A1 -.-> Mem
+    A2 -.-> Mem
+```
+
+## 2. Delegate 6 modes (Delegate 六种模式)
+
+The unified delegate tool and its six execution modes.
+
+```mermaid
+%%{init: {'theme':'base','themeVariables':{'primaryColor':'#F0F5FF','primaryBorderColor':'#007AFF','primaryTextColor':'#1d1d1f','lineColor':'#6e6e73','fontFamily':'-apple-system,SF Pro Text,Noto Sans SC,sans-serif'}}}%%
+flowchart LR
+    classDef system fill:#F0F5FF,stroke:#007AFF,color:#1d1d1f
+    classDef biz    fill:#F0FDF4,stroke:#34C759,color:#1d1d1f
+
+    D("Delegate Tool"):::system
+    D --> S["sync: block & await"]:::biz
+    D --> AS["async: fire & report back"]:::biz
+    D --> W["worker: ephemeral SubAgent"]:::biz
+    D --> F["fan-out: parallel / sequential"]:::biz
+    D --> H["handoff: hand session to user"]:::biz
+    D --> V["via-messaging: fallback wait"]:::biz
+```
+
+## 3. Three-tier conversation memory (三层对话记忆)
+
+active → recent (L0/L1) → archive (L2); writes are dotted
+(`lib/schemas/agent-service/conversation-memory.ts`).
+
+```mermaid
+%%{init: {'theme':'base','themeVariables':{'primaryColor':'#F0F5FF','primaryBorderColor':'#007AFF','primaryTextColor':'#1d1d1f','lineColor':'#6e6e73','fontFamily':'-apple-system,SF Pro Text,Noto Sans SC,sans-serif'}}}%%
+flowchart LR
+    classDef system fill:#F0F5FF,stroke:#007AFF,color:#1d1d1f
+    classDef warn   fill:#FFFBF0,stroke:#FF9500,color:#1d1d1f
+
+    New(["New Message"]):::warn
+    Active[("active: ongoing matters")]:::system
+    Recent[("recent: L0 / L1 summaries")]:::system
+    Archive[("archive: L2 full log")]:::system
+
+    New --> Active
+    Active -.->|compact| Recent
+    Recent -.->|archive after 180d| Archive
+```
+
+## 4. Relation graph (关系图谱，6 种边)
+
+The six edge types projected by `lib/agent-service/relations/projector.ts`, each
+drawn with a distinct edge style. Edge weight decays over time (30-day half-life).
+
+```mermaid
+%%{init: {'theme':'base','themeVariables':{'primaryColor':'#F0F5FF','primaryBorderColor':'#007AFF','primaryTextColor':'#1d1d1f','lineColor':'#6e6e73','fontFamily':'-apple-system,SF Pro Text,Noto Sans SC,sans-serif'}}}%%
+flowchart TD
+    classDef agent fill:#F6F3FF,stroke:#AF52DE,color:#1d1d1f
+    classDef biz   fill:#F0FDF4,stroke:#34C759,color:#1d1d1f
+
+    A1{{"Agent A"}}:::agent
+    A2{{"Agent B"}}:::agent
+    A3{{"Agent C"}}:::agent
+    U(["User"]):::biz
+
+    A1 -->|delegate| A2
+    A1 -.->|mention| A3
+    A2 ===|co_task| A3
+    A2 --o|hierarchy| A1
+    A3 -->|seek_help| A1
+    A1 --x|escalation| U
+```
+
+## Other diagram types
+
+For sequence / state / ER / class diagrams, keep the same `%%{init}%%` header for
+a consistent light theme. Example sequence diagram:
+
+```mermaid
+%%{init: {'theme':'base','themeVariables':{'primaryColor':'#F0F5FF','primaryBorderColor':'#007AFF','primaryTextColor':'#1d1d1f','lineColor':'#6e6e73','fontFamily':'-apple-system,SF Pro Text,Noto Sans SC,sans-serif'}}}%%
+sequenceDiagram
+    actor U as User
+    participant C as DesireCore Core
+    participant A as Sub-Agent
+    participant M as Memory
+    U->>C: request
+    C->>A: delegate (sync)
+    A->>M: write fact
+    A-->>C: result
+    C-->>U: reply
+```