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/semantic-vocabulary.md

@@ -0,0 +1,78 @@
+# Semantic Vocabulary (语义词汇表)
+
+The full mapping from concept → Mermaid shape → DesireCore 3+2 class. Shape and
+color encode meaning, so a reader understands a diagram without a legend.
+
+## The brand header (paste verbatim as the first line of every diagram)
+
+```
+%%{init: {'theme':'base','themeVariables':{'primaryColor':'#F0F5FF','primaryBorderColor':'#007AFF','primaryTextColor':'#1d1d1f','lineColor':'#6e6e73','fontFamily':'-apple-system,SF Pro Text,Noto Sans SC,sans-serif'}}}%%
+```
+
+## The 5 color classes (the only allowed palette)
+
+```
+classDef agent  fill:#F6F3FF,stroke:#AF52DE,color:#1d1d1f
+classDef system fill:#F0F5FF,stroke:#007AFF,color:#1d1d1f
+classDef biz    fill:#F0FDF4,stroke:#34C759,color:#1d1d1f
+classDef warn   fill:#FFFBF0,stroke:#FF9500,color:#1d1d1f
+classDef error  fill:#FFF0F0,stroke:#FF3B30,color:#1d1d1f
+```
+
+`fill` = `cardBgColors`, `stroke` = the 3+2 accent, `color` = `systemColors.label`
+(`#1d1d1f`). Source of truth: `app/theme/tokens/index.ts` and
+`app/theme/presets/agent-colors.ts` **in the DesireCore application codebase**
+(where this skill runs) — these paths are not part of this market repository.
+
+### Class selection rule (mirrors agent-colors.ts)
+
+| Domain | Class | Accent |
+|--------|-------|--------|
+| System / generic (DesireCore core, infra, LLM) | system | blue `#007AFF` |
+| Knowledge / learning (legal, writer, memory) | agent / system | purple `#AF52DE` |
+| Business / execution (data, real-estate, code) | biz | green `#34C759` |
+| Project management / warning / decision | warn | orange `#FF9500` |
+| Error / failure | error | red `#FF3B30` |
+
+Decorative-only colors `yellow #FFCC00` and `teal #5AC8FA` are for background
+gradients elsewhere in the product — never use them in diagrams.
+
+## Shape table
+
+| Concept | Mermaid syntax | Class | Note |
+|---------|----------------|-------|------|
+| Agent / sub-agent | `id{{Name}}` (hexagon) | agent | the signature shape for an autonomous agent |
+| DesireCore core / orchestrator | `id(Name)` (rounded) | system | central coordinator |
+| LLM / model | `id(⚡ Model)` (rounded + ⚡) | system | ⚡ prefix marks an LLM call |
+| Service / tool / skill | `id[Name]` (rect) | biz | a callable capability |
+| Business / execution step | `id[Step]` (rect) | biz | a unit of work |
+| Memory / store / DB | `id[(Store)]` (cylinder) | system | persistent state |
+| User / external actor | `id([User])` (stadium) | biz | the human |
+| Decision / branch | `id{Choice?}` (diamond) | warn | a fork in control flow |
+| External service | `subgraph Ext [External]` ... `end` + `style Ext stroke-dasharray:4 3` | — | dashed boundary = outside the system |
+
+## Arrow / flow encoding
+
+| Flow type | Edge syntax | Meaning |
+|-----------|-------------|---------|
+| Primary data flow | `A --> B` | the main path |
+| Memory write / persistence | `A -.-> B` | dotted = side-effect write |
+| Async event | `A -.->|async| B` | dotted + label |
+| Feedback / retry | `B --> A` (back-edge) | loop |
+| Hierarchy / containment | `A --o B` | circle edge |
+| Hard stop / escalation | `A --x B` | cross edge |
+| Co-participation (equal peers) | `A === B` | thick link |
+
+## Diagram-type cheatsheet
+
+| User intent | Mermaid header |
+|-------------|----------------|
+| Architecture / data flow | `flowchart TD` or `flowchart LR` |
+| Sequence / interaction over time | `sequenceDiagram` |
+| State machine | `stateDiagram-v2` |
+| ER / data model | `erDiagram` |
+| Class / type model | `classDiagram` |
+| Mind map | `mindmap` |
+
+For `sequenceDiagram`, `classDiagram`, etc. that do not support `classDef`, still
+keep the `%%{init}%%` brand header so the theme stays light and on-brand.