feat: implement streaming chat, skill routing, and SAFe PI planning tools

- Add /api/chat/stream endpoint with Server-Sent Events (SSE) for real-time message streaming
  * Implement StreamEvent types (thought, tool_call, tool_result, final, error)
  * Add StreamEventCallback mechanism for event propagation
  * Create StreamChatHandler in webui/bot with proper HTTP headers and flushing

- Implement LLM-based skill router for intelligent capability selection
  * Add optional routerLLM client for semantic routing
  * Implement routeSkillsWithLLM() to match user intent to available skills
  * Add matchSkillsByName() for fuzzy skill matching
  * Update buildUnifiedSystemPrompt() to use routed skills

- Add streaming support to ReAct pipeline
  * Implement runUnifiedReActStream() for streaming thought/action/observation
  * Emit StreamEvent at each ReAct step
  * Support callback error handling in streaming mode

- Integrate three new DevOps tools
  * tools/filedoc: Extract document content from file_id via OpenAI
  * tools/giteaticket: Create Gitea issues from PI plan items with SAFe metadata
  * tools/piplan: Publish PI planning blueprints with dependency tracking

- Add SAFe PI Planning skill
  * Implement PM/SA/RTE (iron triangle) workflow
  * Support for Feature, Enabler, and Dependency definition
  * Automatic task decomposition and Gitea integration

- Create frontend integration documentation
  * Complete SSE protocol specification
  * TypeScript fetch + ReadableStream example
  * LLM-ready refactoring template for other projects

- Simplify file handling
  * Remove legacy file context structures and dual-mode processing
  * Consolidate file operations into UploadAndCacheFiles()
  * Remove FilePromptMode configuration and related complexity

- Update configuration
  * Add Router model support (LLM_ROUTER_MODEL)
  * Add Gitea configuration (BaseURL, Token, Owner, Repo)
  * WebSearch and additional tool infrastructure

Tests: All 22 test packages passing, 8/8 webui tests including 3 new stream tests

configs/env.sample

@@ -17,6 +17,8 @@ TELEGRAM_POLL_TIMEOUT_SECONDS=30
 FEISHU_APP_ID=
 FEISHU_APP_SECRET=
 FEISHU_VERIFY_TOKEN=
+FEISHU_LISTEN_ADDR=:8080
+FEISHU_EVENT_PATH=/feishu/events
 WEBUI_LISTEN_ADDR=:8090
 WEBUI_MAX_UPLOAD_MB=20
 
@@ -24,7 +26,15 @@ LLM_BASE_URL=https://api.openai.com/v1
 LLM_API_KEY=
 LLM_MODEL=gpt-4o-mini
 LLM_FILE_MODEL=gpt-4o-mini
-LLM_FILE_PROMPT_MODE=user_content_file_parts
+LLM_ROUTER_MODEL=
+
+WEB_SEARCH_ENGINE=duckduckgo
+WEB_SEARCH_API_KEY=
+
+GITEA_BASE_URL=
+GITEA_TOKEN=
+GITEA_OWNER=
+GITEA_REPO=
 
 SQLITE_PATH=./data/laodingbot.db
 ALLOWED_DIRS=./workspace,./data,./skills