ILlmFunction.ISeparated.llm to be not null.

[samchon]

Even though no property exists in the LLM side (properties exist only in the Human side), the ILlmFunction.ISeparated.llm property value should be not null for covenience.

This PR enforces the ILlmFunction.ISeparated.llm not to be null.

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This pull request includes several changes aimed at ensuring the llm property always has a defined structure, even when it would otherwise be null. The changes span multiple files and affect both the schema composers and the test files.

Schema Composer Changes:

• src/composers/llm/ChatGptSchemaComposer.ts: Updated the llm property to default to an empty object structure if it is null.
• src/composers/llm/ClaudeSchemaComposer.ts: Modified the separateParameters function to ensure the llm property has a defined structure.
• src/composers/llm/GeminiSchemaComposer.ts: Adjusted the separateParameters function to return a structured llm property.
• src/composers/llm/LlmSchemaV3Composer.ts: Ensured the llm property defaults to an empty object structure if it is null.
• src/composers/llm/LlmSchemaV3_1Composer.ts: Updated the llm property to have a default structure when null.

Structure Changes:

• src/structures/IHttpLlmFunction.ts: Modified the ISeparated interface to ensure the llm property is never null.
• src/structures/ILlmFunction.ts: Updated the ISeparated interface to ensure the llm property always has a defined structure.

Test File Changes:

• test/features/llm/validate_llm_parameters_separate_array.ts: Updated tests to reflect the new default structure of the llm property.
• test/features/llm/validate_llm_parameters_separate_nested.ts: Adjusted tests to ensure the llm property has a defined structure.
• test/features/llm/validate_llm_parameters_separate_object.ts: Modified tests to account for the new default structure of the llm property.
• test/features/llm/validate_llm_parameters_separate_ref.ts: Updated tests to reflect the changes in the llm property structure.
• test/features/llm/validate_llm_schema_separate_string.ts: Adjusted tests to ensure the llm property always has a defined structure.

[samchon]

Test OK.