feat: default formatter_command to npx prettier

Users can now just set format_on_save=true and formatting will work
out of the box (assuming Node.js is installed).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Signed-off-by: Cedric Hurst <cedric@spantree.net>

Author: divideby0

src/basic_memory/config.py

@@ -172,8 +172,8 @@ class BasicMemoryConfig(BaseSettings):
     )
 
     formatter_command: Optional[str] = Field(
-        default=None,
-        description="Default formatter command. Use {file} as placeholder for file path. Example: 'prettier --write {file}'",
+        default="npx prettier --write {file}",
+        description="Default formatter command. Use {file} as placeholder for file path. Uses npx prettier by default.",
     )
 
     formatters: Dict[str, str] = Field(

tests/test_config.py

@@ -498,10 +498,10 @@ def test_format_on_save_can_be_enabled(self):
         config = BasicMemoryConfig(format_on_save=True)
         assert config.format_on_save is True
 
-    def test_formatter_command_defaults_to_none(self):
-        """Test that formatter_command defaults to None."""
+    def test_formatter_command_defaults_to_npx_prettier(self):
+        """Test that formatter_command defaults to npx prettier."""
         config = BasicMemoryConfig()
-        assert config.formatter_command is None
+        assert config.formatter_command == "npx prettier --write {file}"
 
     def test_formatter_command_can_be_set(self):
         """Test that formatter_command can be configured."""

tests/utils/test_file_utils.py

@@ -242,8 +242,8 @@ async def test_format_file_no_formatter_configured(tmp_path: Path):
     test_file = tmp_path / "test.md"
     test_file.write_text("# Test\n")
 
-    config = BasicMemoryConfig(format_on_save=True)
-    # No formatter_command or formatters configured
+    # Explicitly set formatter_command to None to test the "no formatter" case
+    config = BasicMemoryConfig(format_on_save=True, formatter_command=None)
 
     result = await format_file(test_file, config)
     assert result is None