Add ClassDB-based class introspection

[Clubhouse1661]

Problem

Agents cannot inspect a Godot class before creating an instance. node_get_properties requires an existing node, while resource_manage(op="get_info") only supports Resource classes.

Why This Matters

Agents frequently guess outdated or incorrect API names. This causes avoidable failures involving renamed properties, invalid signals, wrong enum values, and incorrect method signatures.

Agents need version-correct API information before creating or modifying anything.

Proposal

Add:

godot://class/{class_name}
api_manage(op="get_class", params={"class_name": "CharacterBody3D"})

Return metadata from the connected editor’s ClassDB:

• Inheritance and instantiability
• Properties with type, hint, hint_string, usage, and available defaults
• Typed methods and signals
• Enums and constants
• Inheriting and concrete classes

Reuse the resource_manage(op="get_info") implementation. Keep it backward compatible and add its currently omitted hint_string.