feat(engine): 添加MCP连接管理和工具集成功能

- 集成MCP连接管理器，支持MCP服务器连接
- 添加多种内置工具：ClarifyTool、CronTool、DelegateTool、ExecuteCodeTool、
  PatchFileTool、ProcessTool、SendMessageTool、SpawnTool、TerminalTool、
  TodoTool、WebFetchTool、WebSearchTool、WriteFileTool等
- 实现工具注册和装配功能
- 添加技能选择上下文参数
- 支持思考模式控制参数thinking_enabled

feat(coordinator): 重构任务执行计划器参数命名

- 将learning_candidate_enabled重命名为allow_candidate_generation
- 更新TeamGraphScheduler中的参数传递
- 修改LocalAgentRunner中的相关参数处理
- 更新README文档中的相应描述

refactor(context): 标准化工具调用参数格式

- 添加_json导入用于参数序列化
- 实现_provider_tool_calls方法标准化OpenAI兼容的工具调用载荷
- 修复工具调用中参数非字符串类型的序列化问题

refactor(session): 优化消息历史记录过滤逻辑

- 修改get_messages_as_conversation为基于运行状态过滤消息
- 排除未完成、失败或错误结束的运行记录
- 改进对话历史的可见性控制机制

fix(store): 修复FTS索引重建逻辑

- 添加异常处理防止FTS索引创建失败
- 实现_rebuild_fts_index方法重新构建全文搜索索引
- 优化索引触发器和表的维护流程

前端改造风格/DESIGN.md

@@ -0,0 +1,411 @@
+# DESIGN.md
+
+## Brand
+
+**Beaver — Taupe**
+
+A calm editorial UI system focused on rhythm, hierarchy, and soft neutral contrast.  
+Designed for AI-native tools, dashboards, and minimalist productivity software.
+
+The interface emphasizes:
+
+- Spacious layouts
+- Soft grayscale surfaces
+- Typography-first hierarchy
+- Rounded geometry
+- Quiet shadows
+- Dense information with low visual noise
+
+The visual tone should feel:
+
+- thoughtful
+- mature
+- calm
+- premium
+- architectural
+- editorial
+
+Avoid:
+
+- saturated colors
+- hard borders
+- sharp corners
+- excessive gradients
+- loud shadows
+- playful illustration-heavy UI
+
+---
+
+# Colors
+
+## Core Palette
+
+| Token | Hex | Usage |
+|---|---|---|
+| background | `#F5F3F1` | Main app background |
+| foreground | `#0B0B0B` | Primary text |
+| primary | `#1D1715` | Primary actions |
+| secondary | `#E5E2DF` | Secondary surfaces |
+| muted | `#DDD9D6` | Muted backgrounds |
+| accent | `#CAC5C0` | Borders / subtle emphasis |
+
+---
+
+## Neutral Scale
+
+| Token | Hex |
+|---|---|
+| zinc-50 | `#F7F5F4` |
+| zinc-100 | `#ECE8E5` |
+| zinc-200 | `#D8D2CE` |
+| zinc-300 | `#B8AEA8` |
+| zinc-400 | `#8B7E77` |
+| zinc-500 | `#6A5E58` |
+| zinc-600 | `#4F4642` |
+| zinc-700 | `#342E2B` |
+
+---
+
+## Semantic Colors
+
+### Taupe
+
+| Step | Hex |
+|---|---|
+| taupe-100 | `#E7E2DE` |
+| taupe-300 | `#B8AEA8` |
+| taupe-500 | `#8B7E77` |
+| taupe-700 | `#5F5550` |
+
+### Sage
+
+| Step | Hex |
+|---|---|
+| sage-100 | `#E3E8E2` |
+| sage-300 | `#B7C2B5` |
+| sage-500 | `#869683` |
+| sage-700 | `#657162` |
+
+### Slate
+
+| Step | Hex |
+|---|---|
+| slate-100 | `#E4E7EB` |
+| slate-300 | `#BCC4CE` |
+| slate-500 | `#8C96A3` |
+| slate-700 | `#697281` |
+
+---
+
+# Typography
+
+## Philosophy
+
+Typography drives hierarchy.
+
+The system should feel like a modern editorial publication mixed with a productivity dashboard.
+
+Large headings use elegant serif typography.  
+UI and body copy use neutral grotesk sans-serif typography.
+
+---
+
+## Font Stack
+
+### Serif
+
+```css
+font-family: "Lora", Georgia, serif;
+```
+
+Used for:
+
+- hero titles
+- article headings
+- marketing emphasis
+- editorial sections
+
+---
+
+### Sans
+
+```css
+font-family: "Public Sans", Inter, sans-serif;
+```
+
+Used for:
+
+- UI
+- labels
+- forms
+- dashboards
+- buttons
+- navigation
+
+---
+
+## Type Scale
+
+| Style | Size | Weight | Line Height |
+|---|---|---|---|
+| h1 | 48px | 600 | 1.1 |
+| h2 | 36px | 600 | 1.15 |
+| h3 | 28px | 500 | 1.2 |
+| body-lg | 18px | 400 | 1.7 |
+| body | 16px | 400 | 1.6 |
+| small | 14px | 400 | 1.5 |
+| mono | 13px | 500 | 1.4 |
+
+---
+
+# Radius
+
+Rounded geometry should feel soft but architectural.
+
+| Token | Radius |
+|---|---|
+| xs | 4px |
+| sm | 8px |
+| md | 12px |
+| lg | 16px |
+| xl | 24px |
+| full | 999px |
+
+Cards should primarily use:
+
+```css
+border-radius: 16px;
+```
+
+---
+
+# Shadows
+
+Shadows should be subtle and diffused.
+
+Avoid strong elevation.
+
+## Soft
+
+```css
+box-shadow:
+0 1px 2px rgba(0,0,0,0.04),
+0 6px 24px rgba(0,0,0,0.03);
+```
+
+## Floating
+
+```css
+box-shadow:
+0 12px 40px rgba(0,0,0,0.06);
+```
+
+---
+
+# Grid
+
+## Layout
+
+- 12-column grid
+- Max width: `1280px`
+- Horizontal padding: `32px`
+- Large whitespace between sections
+
+---
+
+## Content Widths
+
+| Type | Width |
+|---|---|
+| reading | 720px |
+| dashboard | 1280px |
+| modal | 480px |
+| form | 560px |
+
+---
+
+# Spacing
+
+Base unit:
+
+```txt
+4px
+```
+
+Spacing scale:
+
+| Token | Value |
+|---|---|
+| 1 | 4px |
+| 2 | 8px |
+| 3 | 12px |
+| 4 | 16px |
+| 5 | 20px |
+| 6 | 24px |
+| 8 | 32px |
+| 10 | 40px |
+| 12 | 48px |
+| 16 | 64px |
+
+Use generous vertical rhythm.
+
+Sections should breathe.
+
+---
+
+# Components
+
+## Buttons
+
+### Primary
+
+- Dark background
+- White text
+- Pill radius
+- Minimal shadow
+
+```css
+background: #1D1715;
+color: white;
+border-radius: 999px;
+height: 40px;
+padding: 0 16px;
+```
+
+### Secondary
+
+```css
+background: #ECE8E5;
+color: #1D1715;
+```
+
+### Ghost
+
+Transparent background with subtle hover fill.
+
+---
+
+## Cards
+
+Cards are soft containers with quiet separation.
+
+```css
+background: rgba(255,255,255,0.7);
+border: 1px solid rgba(0,0,0,0.04);
+border-radius: 16px;
+```
+
+Avoid heavy borders.
+
+---
+
+## Inputs
+
+Inputs should feel invisible until focused.
+
+```css
+background: #F7F5F4;
+border: 1px solid transparent;
+```
+
+Focus:
+
+```css
+border-color: #8B7E77;
+box-shadow: 0 0 0 3px rgba(139,126,119,0.12);
+```
+
+---
+
+## Charts
+
+Charts should use muted earthy tones.
+
+Preferred palette:
+
+- taupe
+- sage
+- slate
+
+Avoid:
+
+- neon colors
+- bright blue dashboards
+- rainbow charts
+
+---
+
+# Motion
+
+Motion should be restrained and smooth.
+
+Preferred easing:
+
+```css
+cubic-bezier(0.22, 1, 0.36, 1)
+```
+
+Preferred duration:
+
+| Type | Duration |
+|---|---|
+| hover | 150ms |
+| panel | 250ms |
+| modal | 350ms |
+
+---
+
+# Layout Skeleton
+
+Application layout:
+
+- Left sidebar
+- Large content canvas
+- Floating top toolbar
+- Soft dashboard cards
+- Spacious internal padding
+
+The UI should always feel:
+
+- breathable
+- editorial
+- premium
+- calm
+
+Never dense or overly enterprise-looking.
+
+---
+
+# Design Keywords
+
+Use these words when generating UI:
+
+- editorial
+- taupe
+- soft neutral
+- premium minimal
+- typography-first
+- architectural spacing
+- calm dashboard
+- quiet luxury
+- modern serif
+- subtle shadows
+- muted grayscale
+- sophisticated SaaS
+
+---
+
+# AI Agent Instructions
+
+When generating UI:
+
+1. Prioritize whitespace over density
+2. Typography should create hierarchy
+3. Use muted neutral palettes
+4. Prefer soft cards over hard sections
+5. Avoid excessive color usage
+6. Keep interactions subtle
+7. Use serif fonts sparingly for emphasis
+8. Maintain premium visual restraint
+9. Design should feel timeless rather than trendy
+10. Every screen should feel breathable