Add tests for contextseek tools output formats

[Evenss]

Description

The CLI supports contextseek tools --format openai and --format anthropic, but these output contracts are not well covered by tests.

Related code:

• https://github.com/ob-labs/contextseek/blob/main/src/contextseek/cli/main.py
• https://github.com/ob-labs/contextseek/tree/main/tests/unit_tests

Please add focused tests that verify the command returns valid tool definitions.

Acceptance criteria:

• Test OpenAI-format output is valid JSON and includes expected tool definitions.
• Test Anthropic-format output is valid JSON and includes expected tool definitions.
• Tests should not require external services.