feat(agents): Phase 6 tool system refactoring

Phase 6.1: ToolRegistry infrastructure
- Add ToolManifest with ToolCategory, PermissionClass, SideEffectScope
- Add ToolRegistry singleton with register/get/unregister/list/search
- Add BaseTool abstract class with ReadTool/WriteTool/DBWriteTool/ExternalTool/NetworkTool subclasses
- Add migration layer for backward compatibility

Phase 6.2: Hook interception system
- Add HookType (PRE_TOOL_USE, POST_TOOL_USE, TOOL_ERROR, TOOL_SKIP)
- Add HookManager with singleton for hook registration
- Add HookExecutor for pre/post/error hook execution

Phase 6.3: Streaming execution
- Add StreamingToolExecutor with batch execution support

Phase 6.4: New builtin tools
- Add file_tools: GlobTool, GrepTool, ReadFileTool, WriteFileTool
- Add system_tools: BashTool, PowerShellTool
- Add dev_tools: LSPTools, GitTool
- Add collaboration_tools: TeamAgentTool, TaskBroadcastTool

Tests: 29 passed

backend/app/agents/tools/builtins/__init__.py

@@ -0,0 +1,43 @@
+"""内置工具集 - Phase 6.4
+
+新的内置工具，使用 BaseTool 基类。
+"""
+
+from app.agents.tools.builtins.file_tools import (
+    GlobTool,
+    GrepTool,
+    ReadFileTool,
+    WriteFileTool,
+)
+
+from app.agents.tools.builtins.system_tools import (
+    BashTool,
+    PowerShellTool,
+)
+
+from app.agents.tools.builtins.dev_tools import (
+    LSPTools,
+    GitTool,
+)
+
+from app.agents.tools.builtins.collaboration_tools import (
+    TeamAgentTool,
+    TaskBroadcastTool,
+)
+
+__all__ = [
+    # File tools
+    "GlobTool",
+    "GrepTool",
+    "ReadFileTool",
+    "WriteFileTool",
+    # System tools
+    "BashTool",
+    "PowerShellTool",
+    # Dev tools
+    "LSPTools",
+    "GitTool",
+    # Collaboration tools
+    "TeamAgentTool",
+    "TaskBroadcastTool",
+]