fix(cli): use callback pattern to avoid breaking no-subcommand invocation

Registering a second @app.command() forced Typer to require an explicit
subcommand, breaking the existing `python -m webwright.run.cli -t "..."`
invocation form. Switch `main` to @app.callback(invoke_without_command=True)
so the default invocation works without a subcommand while list-configs
remains available as an explicit subcommand.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: nuthalapativarun

src/webwright/run/cli.py

@@ -16,7 +16,7 @@
 
 DEFAULT_CONFIGS = ["base.yaml", "model_openai.yaml"]
 
-app = typer.Typer(no_args_is_help=True)
+app = typer.Typer()
 console = Console(highlight=False)
 
 
@@ -142,15 +142,21 @@ def list_configs() -> None:
         console.print(path.name)
 
 
-@app.command()
+@app.callback(invoke_without_command=True)
 def main(
-    task: str = typer.Option(..., "-t", "--task", help="Natural language task description."),
+    ctx: typer.Context,
+    task: str | None = typer.Option(None, "-t", "--task", help="Natural language task description."),
     task_id: str | None = typer.Option(None, "--task-id", help="Optional identifier used in the output directory name."),
     start_url: str | None = typer.Option(None, "--start-url", help="Optional starting URL for the task."),
     config_spec: list[str] = typer.Option(DEFAULT_CONFIGS, "-c", "--config"),
     output_dir: Path | None = typer.Option(None, "-o", "--output-dir"),
     debug: bool = typer.Option(False, "--debug", help="Launch headed local Playwright with devtools and keep it open for inspection."),
 ) -> Any:
+    if ctx.invoked_subcommand is not None:
+        return
+    if task is None:
+        console.print(ctx.get_help())
+        raise typer.Exit()
     return run_one(
         task=task,
         task_id=task_id,