Node and Python bindings silently accept invalid output formats

Description

The Node and Python bindings accept unsupported output-format strings and silently resolve them to JSON. This differs from the WASM binding, which rejects unsupported values, and makes configuration typos difficult to detect.

Reproduction

Node.js:

const parser = new LiteParse({ outputFormat: "yaml" });
console.log(parser.config.outputFormat); // "json"

Python:

parser = LiteParse(output_format="yaml")
print(parser.config.output_format)  # "json"

Expected behavior

Constructing a parser with an unsupported output format should fail with a clear error. Supported values are json, text, markdown, and the existing md alias.

Actual behavior

Any unrecognized value falls through to OutputFormat::Json.

Impact

A misspelled or unsupported format silently produces JSON instead of alerting the caller, potentially causing downstream processing to receive the wrong representation.