feat(runner): graceful shutdown for provider CLI processes

feat(config): add .env file support via dotenv

docs(readme): add active development status notice

feat(commands): add /exit and !exit to end channel session

docs(legal): add Terms of Service with security disclosure

docs(readme): add motivation section about iMessage-inspired workflow

docs(readme): restructure README with EN/KO bilingual support

docs(github): add issue templates

docs(readme): replace personal paths and expand user-friendly guide

chore(security): harden local ignore rules

docs: add updated usage guides and provider-to-llm flowchart

chore(license): add MIT license file

feat(core): add provider adapter architecture and provider-aware run flow