feat: add Braille spinner, shell completions, and TUI polish

- Add with_spinner context manager with cyan Braille animation for human mode.
- Wrap all query/execution commands in cli.py with loading spinners.
- Integrate shtab: auto-install shell completions during init for zsh/bash.
- Add `completion` subcommand for manual script generation.
- Fix stale output_format default in DEFAULT_CONFIG (json → tui).
- Add help descriptions to all second-level subcommands.
- Version 2.0.4.

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

tests/test_cli.py

@@ -20,11 +20,14 @@ class CLITestCase(unittest.TestCase):
     def test_init_dispatches(self):
         captured = {}
         with patch.object(cli, "ensure_init_files", return_value={"force": True, "root": "/tmp/ch"}), patch.object(
+            cli, "install_shell_completion", return_value={"shell": "zsh", "installed": True, "path": "/tmp/ch/_coinhunter"}
+        ), patch.object(
             cli, "print_output", side_effect=lambda payload, **kwargs: captured.setdefault("payload", payload)
         ):
             result = cli.main(["init", "--force"])
         self.assertEqual(result, 0)
         self.assertTrue(captured["payload"]["force"])
+        self.assertIn("completion", captured["payload"])
 
     def test_old_command_is_rejected(self):
         with self.assertRaises(SystemExit):