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/cli/main.py

@@ -0,0 +1,64 @@
+"""
+Webber CLI main entry point.
+
+Usage:
+    webber --help
+    webber --version
+    webber chat [OPTIONS]
+    webber explore QUERY [OPTIONS]
+"""
+import typer
+from rich.console import Console
+
+from src.shared.config import get_settings
+
+# Create Typer app
+app = typer.Typer(
+    name="webber",
+    help="Multi-Agent AI Development System",
+    no_args_is_help=True,
+    add_completion=False,
+)
+
+console = Console()
+
+
+def version_callback(value: bool) -> None:
+    """Display version and exit."""
+    if value:
+        settings = get_settings()
+        console.print(f"[bold blue]{settings.app_name}[/] version [green]{settings.app_version}[/]")
+        console.print(f"[dim]{settings.app_description}[/]")
+        raise typer.Exit()
+
+
+@app.callback()
+def main(
+    version: bool = typer.Option(
+        False,
+        "--version",
+        "-v",
+        callback=version_callback,
+        is_eager=True,
+        help="Show version and exit",
+    ),
+) -> None:
+    """
+    Webber - Multi-Agent AI Development System.
+
+    A CLI tool for codebase exploration and development assistance
+    powered by local LLMs via Ollama.
+    """
+    pass
+
+
+# Import and register commands
+from src.cli.commands import chat, explore, version  # noqa: E402, F401
+
+# Register subcommands
+app.command(name="chat")(chat.chat_command)
+app.command(name="explore")(explore.explore_command)
+
+
+if __name__ == "__main__":
+    app()