feat: make chat the default command

Running 'webber-cli' without arguments now starts chat mode.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

webber-cli/webber_cli/main.py

@@ -99,7 +99,8 @@ def create_prompt_session(working_dir: str) -> PromptSession:
 app = typer.Typer(
     name="webber-cli",
     help="CLI client for the Webber API",
-    no_args_is_help=True,
+    no_args_is_help=False,
+    invoke_without_command=True,
     add_completion=False,
 )
 
@@ -141,8 +142,9 @@ def _confirm_auto_accept() -> bool:
     )
 
 
-@app.callback()
+@app.callback(invoke_without_command=True)
 def main(
+    ctx: typer.Context,
     version: bool = typer.Option(
         False,
         "--version",
@@ -153,7 +155,15 @@ def main(
     ),
 ) -> None:
     """Webber CLI - Talk to the Webber API."""
-    pass
+    # Default to chat command if no subcommand given
+    if ctx.invoked_subcommand is None:
+        chat(
+            directory=".",
+            api_url=None,
+            mode=None,
+            resume=None,
+            stream=None,
+        )
 
 
 @app.command()