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/agents/schemas.py

@@ -0,0 +1,30 @@
+"""
+Request and response schemas for agent API.
+"""
+from src.shared.base import BaseSchema
+
+
+class AgentRunRequest(BaseSchema):
+    """Request to run an agent."""
+    prompt: str
+    working_dir: str = "."
+    agent_type: str = "explore"
+
+
+class AgentRunResponse(BaseSchema):
+    """Response from agent execution."""
+    response: str
+    agent_type: str
+    success: bool = True
+    error: str | None = None
+
+
+class AgentInfo(BaseSchema):
+    """Information about an agent."""
+    name: str
+    description: str
+
+
+class AgentListResponse(BaseSchema):
+    """List of available agents."""
+    agents: list[AgentInfo]