docs: configuration.md documents non-existent ConfigValue class

[zeevdr]

Description

sdk/docs/configuration.md:209-216 documents a ConfigValue dataclass (fields field_path, value, checksum, description) that does not exist in the package; get_all() returns dict[str, str]. A reader importing it gets an ImportError.

Acceptance criteria

• Remove the ConfigValue block from configuration.md.
• Document the real third dataclass (ServerVersion) and clarify that get_all() returns dict[str, str].

Source: documentation review, 2026-06-07.