docs(01-03): complete error handler & config manager plan

- Structured error types with rich context (KBError, NetworkError, etc.)
- Configuration management via pydantic-settings from ~/.kb_env
- Automatic retry mechanism with tenacity (3 attempts, exponential backoff)
- All 100 tests passing
- Requirements REL-02, MNT-02, MNT-03 completed

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.planning/REQUIREMENTS.md

@@ -16,7 +16,7 @@ Requirements for initial release. Each maps to roadmap phases.
 ### Reliability (可靠性)
 
 - [x] **REL-01**: 幂等执行保证 - 重复执行同一链接不会产生重复文件或重复处理
-- [ ] **REL-02**: 错误恢复策略 - 403/超时/网络错误有明确的降级策略和重试机制
+- [x] **REL-02**: 错误恢复策略 - 403/超时/网络错误有明确的降级策略和重试机制
 - [x] **REL-03**: 清晰的流程定义 - 每个步骤的前置条件、输出格式、成功标准明确
 
 ### Validation (验证)
@@ -26,8 +26,8 @@ Requirements for initial release. Each maps to roadmap phases.
 ### Maintainability (可维护性)
 
 - [ ] **MNT-01**: 代码结构清晰化 - 模块化设计，新人能快速理解和修改
-- [ ] **MNT-02**: 统一配置管理 - 环境变量集中在 ~/.kb_env，使用 pydantic-settings 管理
-- [ ] **MNT-03**: 结构化错误处理 - 错误包含上下文信息，便于调试和日志追踪
+- [x] **MNT-02**: 统一配置管理 - 环境变量集中在 ~/.kb_env，使用 pydantic-settings 管理
+- [x] **MNT-03**: 结构化错误处理 - 错误包含上下文信息，便于调试和日志追踪
 
 ### Platform Support (平台支持)
 
@@ -73,11 +73,11 @@ Which phases cover which requirements. Updated during roadmap creation.
 | PIPE-02 | Phase 1 | Complete |
 | PIPE-03 | Phase 1 | Complete |
 | REL-01 | Phase 1 | Complete |
-| REL-02 | Phase 1 | Pending |
+| REL-02 | Phase 1 | Complete |
 | REL-03 | Phase 1 | Complete |
 | VAL-01 | Phase 1 | Complete |
-| MNT-02 | Phase 1 | Pending |
-| MNT-03 | Phase 1 | Pending |
+| MNT-02 | Phase 1 | Complete |
+| MNT-03 | Phase 1 | Complete |
 | PLAT-01 | Phase 2 | Pending |
 | PLAT-02 | Phase 2 | Pending |
 | PLAT-03 | Phase 2 | Pending |