feat(tools): add ShellTool + WebSearchTool, memory system, onboarding wizard, chat mode
- ShellTool: safe command execution with allowlist, blocked patterns (regex), timeout, output truncation
- WebSearchTool: multi-backend search with Tavily → Serper → DuckDuckGo Lite fallback
- MemoryTool: agent-callable tool with add/replace/remove/read actions
- MemoryStore/MemoryFile: file-based memory (SOUL.md, USER.md, MEMORY.md, DAILY.md)
- Onboarding wizard: provider selection, API key, model selection, agent personality
- Chat mode: interactive CLI with streaming, memory injection, tool integration
- Add 百炼 Coding Plan provider with 10 models
- 102 unit tests (34 new for ShellTool + WebSearchTool)
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