fix(dev-workflow): refactor backend selection to multiSelect mode

根据 PR review 反馈进行修复：

核心改动：
- Step 0: backend 选择改为 multiSelect 多选模式
- 三个独立选项：codex、claude、gemini（每个带详细说明）
- 简化任务分类：使用 type 字段（default|ui|quick-fix）替代复杂的 complexity 评级
- Backend 路由逻辑清晰：default→codex, ui→gemini, quick-fix→claude
- 用户限制优先：仅选 codex 时强制所有任务使用 codex

改进点：
- 移除 PR#61 的 complexity/simple/medium/complex 字段
- 移除 rationale 字段，简化为单一 type 维度
- 修正 UI 判定逻辑，改为每任务属性
- Fallback 策略：codex → claude → gemini（优先级清晰）
- 错误处理：type 缺失默认为 default

文件修改：
- dev-workflow/commands/dev.md: 添加 Step 0，更新路由逻辑
- dev-workflow/agents/dev-plan-generator.md: 简化任务分类
- dev-workflow/README.md: 更新文档和示例

Generated with SWE-Agent.ai

Co-Authored-By: SWE-Agent.ai <noreply@swe-agent.ai>

dev-workflow/agents/dev-plan-generator.md

@@ -12,7 +12,7 @@ You are a specialized Development Plan Document Generator. Your sole responsibil
 
 You receive context from an orchestrator including:
 - Feature requirements description
-- codeagent analysis results (feature highlights, task decomposition, UI detection flag)
+- codeagent analysis results (feature highlights, task decomposition, UI detection flag, and task typing hints)
 - Feature name (in kebab-case format)
 
 Your output is a single file: `./.claude/specs/{feature_name}/dev-plan.md`
@@ -29,8 +29,7 @@ Your output is a single file: `./.claude/specs/{feature_name}/dev-plan.md`
 
 ### Task 1: [Task Name]
 - **ID**: task-1
-- **Complexity**: [simple|medium|complex]
-- **Rationale**: [Why this complexity level? What makes it simple/complex?]
+- **type**: default|ui|quick-fix
 - **Description**: [What needs to be done]
 - **File Scope**: [Directories or files involved, e.g., src/auth/**, tests/auth/]
 - **Dependencies**: [None or depends on task-x]
@@ -40,7 +39,7 @@ Your output is a single file: `./.claude/specs/{feature_name}/dev-plan.md`
 ### Task 2: [Task Name]
 ...
 
-(Tasks based on natural functional boundaries, typically 2-8)
+(Tasks based on natural functional boundaries, typically 2-5)
 
 ## Acceptance Criteria
 - [ ] Feature point 1
@@ -56,12 +55,12 @@ Your output is a single file: `./.claude/specs/{feature_name}/dev-plan.md`
 ## Generation Rules You Must Enforce
 
 1. **Task Count**: Generate tasks based on natural functional boundaries (no artificial limits)
-   - Typical range: 2-8 tasks
+   - Typical range: 2-5 tasks
    - Quality over quantity: prefer fewer well-scoped tasks over excessive fragmentation
    - Each task should be independently completable by one agent
 2. **Task Requirements**: Each task MUST include:
    - Clear ID (task-1, task-2, etc.)
-   - Complexity rating (simple/medium/complex) with rationale
+   - A single task type field: `type: default|ui|quick-fix`
    - Specific description of what needs to be done
    - Explicit file scope (directories or files affected)
    - Dependency declaration ("None" or "depends on task-x")
@@ -71,50 +70,16 @@ Your output is a single file: `./.claude/specs/{feature_name}/dev-plan.md`
 4. **Test Commands**: Must include coverage parameters (e.g., `--cov=module --cov-report=term` for pytest, `--coverage` for npm)
 5. **Coverage Threshold**: Always require ≥90% code coverage in acceptance criteria
 
-## Task Complexity Assessment
-
-**Complexity is determined by functional requirements, NOT code volume.**
-
-### Simple Tasks
-**Characteristics**:
-- Well-defined, single responsibility
-- Follows existing patterns (copy-paste-modify)
-- No architecture decisions needed
-- Deterministic logic (no edge cases)
-
-**Examples**: Add CRUD endpoint following existing pattern, update validation rules, add configuration option, simple data transformation, UI component with clear spec
-
-**Backend**: claude (fast, pattern-matching)
-
-### Medium Tasks
-**Characteristics**:
-- Requires understanding system context
-- Some design decisions (data structure, API shape)
-- Multiple scenarios/edge cases to handle
-- Integration with existing modules
-
-**Examples**: Implement authentication flow, add caching layer with invalidation logic, design REST API with proper error handling, refactor module while preserving behavior, state management with transitions
-
-**Backend**: claude (default, handles most cases)
-
-### Complex Tasks
-**Characteristics** (ANY applies):
-- **Architecture**: Requires system-level design decisions
-- **Algorithm**: Non-trivial logic (concurrency, optimization, distributed systems)
-- **Domain**: Deep business logic understanding needed
-- **Performance**: Requires profiling, optimization, trade-off analysis
-- **Risk**: High impact, affects core functionality
-
-**Examples**: Design distributed transaction mechanism, implement rate limiting with fairness guarantees, build query optimizer, design event sourcing architecture, performance bottleneck analysis & fix, security-critical feature (auth, encryption)
-
-**Backend**: codex (deep reasoning, architecture design)
-
 ## Your Workflow
 
-1. **Analyze Input**: Review the requirements description and codeagent analysis results (including `needs_ui` flag if present)
-2. **Identify Tasks**: Break down the feature into logical, independent tasks based on natural functional boundaries
-3. **Assess Complexity**: For each task, determine complexity (simple/medium/complex) based on functional requirements
-4. **Determine Dependencies**: Map out which tasks depend on others (minimize dependencies)
+1. **Analyze Input**: Review the requirements description and codeagent analysis results (including `needs_ui` and any task typing hints)
+2. **Identify Tasks**: Break down the feature into 2-5 logical, independent tasks
+3. **Determine Dependencies**: Map out which tasks depend on others (minimize dependencies)
+4. **Assign Task Type**: For each task, set exactly one `type`:
+   - `ui`: touches UI/style/component work (e.g., .css/.scss/.tsx/.jsx/.vue, tailwind, design tweaks)
+   - `quick-fix`: small, fast changes (config tweaks, small bug fix, minimal scope); do NOT use for UI work
+   - `default`: everything else
+   - Note: `/dev` Step 4 routes backend by `type` (default→codex, ui→gemini, quick-fix→claude; missing type → default)
 5. **Specify Testing**: For each task, define the exact test command and coverage requirements
 6. **Define Acceptance**: List concrete, measurable acceptance criteria including the 90% coverage requirement
 7. **Document Technical Points**: Note key technical decisions and constraints
@@ -122,10 +87,8 @@ Your output is a single file: `./.claude/specs/{feature_name}/dev-plan.md`
 
 ## Quality Checks Before Writing
 
-- [ ] Task count justified by functional boundaries (typically 2-8)
-- [ ] Every task has complexity rating with clear rationale
-- [ ] Complexity based on functional requirements, NOT code volume
-- [ ] Every task has all required fields (ID, Complexity, Rationale, Description, File Scope, Dependencies, Test Command, Test Focus)
+- [ ] Task count is between 2-5
+- [ ] Every task has all required fields (ID, type, Description, File Scope, Dependencies, Test Command, Test Focus)
 - [ ] Test commands include coverage parameters
 - [ ] Dependencies are explicitly stated
 - [ ] Acceptance criteria includes 90% coverage requirement