feat: add cleanco skill

[00al]

Summary

• Add new cleanco skill that cleans company names for cold email outreach using OpenAI's gpt-4o-mini model
• Removes legal suffixes (Inc, LLC, Ltd, GmbH, etc.), parenthetical descriptions, pipe/colon-separated taglines while preserving brand names
• Provides a cleanco.company_name transform for use in workflows, plus CLI commands (clean, cache, show) for standalone CSV cleaning
• Results are cached in a local SQLite database so each unique name is only cleaned once
• Adds cleanco config template to openkiln/commands/skill.py

Files changed

• openkiln/skills/cleanco/ — new skill directory (api, cli, queries, workflow, schema, skill.toml, SKILL.md)
• openkiln/commands/skill.py — added cleanco config template

Test plan

• ruff check passes (fixed unused import, import sorting, f-string, and line-length issues)
• ruff format passes
• Full test suite passes (152 tests, excluding pre-existing test_api_client_no_key_error failures)

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