Complete SAND-WP-0001: bootstrap Python dev workflow

Scaffold sandboxer package (src layout, typer CLI stub, pytest, ruff),
Makefile targets, and document install/test/lint/build commands in
AGENTS.md and stack-and-commands.md. Mark bootstrap workplan finished.

src/sandboxer/__init__.py

@@ -0,0 +1,3 @@
+"""sand-boxer — sandbox provisioning meta-framework."""
+
+__version__ = "0.0.0"

src/sandboxer/api/__init__.py

@@ -0,0 +1 @@
+"""HTTP API layer (planned in SAND-WP-0002)."""

src/sandboxer/cli.py

@@ -0,0 +1,26 @@
+"""CLI entry point (bootstrap stub; expanded in SAND-WP-0002)."""
+
+import typer
+
+from sandboxer import __version__
+
+app = typer.Typer(
+    name="sandboxer",
+    help="Provision and manage isolated sandbox environments.",
+    no_args_is_help=True,
+)
+
+
+@app.callback()
+def main() -> None:
+    """sand-boxer CLI root."""
+
+
+@app.command()
+def version() -> None:
+    """Print the installed package version."""
+    typer.echo(__version__)
+
+
+if __name__ == "__main__":
+    app()

src/sandboxer/extensions/__init__.py

@@ -0,0 +1 @@
+"""Extension registry and backend adapters."""

src/sandboxer/lifecycle/__init__.py

@@ -0,0 +1 @@
+"""Sandbox lifecycle and State Hub registration."""

src/sandboxer/profiles/__init__.py

@@ -0,0 +1 @@
+"""Sandbox profile catalog and validation."""