feat(cli): add CLI entry point with version command

Initialise Typer app with --version flag and help text.

src/veritext/cli/__init__.py

@@ -0,0 +1,5 @@
+"""CLI module: Command-line interface for Veritext."""
+
+from veritext.cli.main import app
+
+__all__ = ["app"]

src/veritext/cli/main.py

@@ -0,0 +1,31 @@
+"""Veritext CLI entry point."""
+
+import typer
+
+import veritext
+
+app = typer.Typer(
+    name="veritext",
+    help="Semantic text validation framework.",
+    no_args_is_help=True,
+)
+
+
+@app.callback(invoke_without_command=True)
+def main(
+    version: bool | None = typer.Option(
+        None,
+        "--version",
+        "-V",
+        help="Show version and exit.",
+        is_eager=True,
+    ),
+) -> None:
+    """Veritext: Semantic text validation framework for Python."""
+    if version:
+        typer.echo(f"veritext {veritext.__version__}")
+        raise typer.Exit()
+
+
+if __name__ == "__main__":
+    app()