refactor: reorganize into monorepo with separate subprojects

Structure webber into three independent subprojects:
- webber-api/: FastAPI backend server with all agent code
- webber-cli/: Standalone CLI client (renamed from cli/ to webber_cli/)
- webber-sandbox/: Test project for functional testing

Key changes:
- Each subproject has its own .venv (Python 3.12+)
- Added sandbox.sh for managing test project templates
- Created sandbox-templates/ with calculator-cli and empty starter
- Updated CI/CD for prefixed tags (api/v*, cli/v*)
- Added comprehensive AGENTS.md with operational instructions
- Added gitignore filtering to glob and grep tools
- Created pyproject.toml for each subproject

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

webber-api/src/domains/tools/__init__.py

@@ -0,0 +1,18 @@
+"""
+Tool implementations for agent use.
+
+All tools inherit from BaseTool and return ToolResult.
+"""
+from src.domains.tools.base import BaseTool, ToolResult
+from src.domains.tools.file import ReadFileTool, GlobFilesTool
+from src.domains.tools.search import GrepContentTool
+from src.domains.tools.shell import BashReadOnlyTool
+
+__all__ = [
+    "BaseTool",
+    "ToolResult",
+    "ReadFileTool",
+    "GlobFilesTool",
+    "GrepContentTool",
+    "BashReadOnlyTool",
+]