feat(cli): make bot_bottle.cli runnable with python -m

`python -m bot_bottle.cli` failed with "is a package and cannot be
directly executed" — the package had a `if __name__ == "__main__"` block
in `__init__.py`, which never fires for a package and made the invocation
look supported when it wasn't. Add a real `__main__.py` and drop the dead
block.

Matters for `bb login`, whose docstring documents a `bb` entry point that
nothing installs; `-m` is the closest thing to it until there's a
console-script.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bot_bottle/cli/__init__.py

@@ -114,7 +114,3 @@ def main(argv: list[str] | None = None) -> int:
         return e.code if isinstance(e.code, int) else 1
     except KeyboardInterrupt:
         return 130
-
-
-if __name__ == "__main__":
-    sys.exit(main())

bot_bottle/cli/__main__.py

@@ -0,0 +1,15 @@
+"""Entry point for `python -m bot_bottle.cli`.
+
+`cli.py` at the repo root is the usual way in; this makes the package
+runnable too, so the CLI works from an installed copy where there is no
+`cli.py` on disk to point at.
+"""
+
+from __future__ import annotations
+
+import sys
+
+from . import main
+
+if __name__ == "__main__":
+    sys.exit(main())

tests/unit/test_cli_module_entry.py

@@ -0,0 +1,40 @@
+"""The CLI package is runnable as `python -m bot_bottle.cli`."""
+
+from __future__ import annotations
+
+import subprocess
+import sys
+import unittest
+from pathlib import Path
+
+_REPO_ROOT = Path(__file__).resolve().parents[2]
+
+
+def _run(*args: str) -> subprocess.CompletedProcess[str]:
+    return subprocess.run(
+        [sys.executable, "-m", "bot_bottle.cli", *args],
+        cwd=_REPO_ROOT,
+        capture_output=True,
+        text=True,
+        check=False,
+    )
+
+
+class TestModuleEntry(unittest.TestCase):
+    def test_help_exits_zero(self) -> None:
+        result = _run("--help")
+        self.assertEqual(result.returncode, 0, result.stderr)
+        self.assertIn("login", result.stderr)
+
+    def test_no_args_prints_usage(self) -> None:
+        # main() returns 2 with no command, matching the cli.py entry point.
+        self.assertEqual(_run().returncode, 2)
+
+    def test_subcommand_help_reaches_handler(self) -> None:
+        result = _run("login", "--help")
+        self.assertEqual(result.returncode, 0, result.stderr)
+        self.assertIn("--console-url", result.stderr)
+
+
+if __name__ == "__main__":
+    unittest.main()