v0.18.0

Full command-surface overhaul: ask now plans knowledge-graph retrieval with the LLM and answers by default (--no-llm opts out; raw and explicit-backend retrieval moved to query); the engine writes daily session chunks for ~20x faster time-range recall with a parity-guaranteed raw fallback; new tesserae doctor runs 20 health checks with safe --fix repairs; init becomes the single onboarding step with credentialed LLM-CLI detection and custom claude-compatible endpoints; cognee is demoted to an opt-in extra (codex_cognify removed); and an adversarial pass renamed or removed every misleading flag across all 26 commands — each old spelling prints its replacement and exits 2. Full notes: docs/release-notes/v0.18.0.md (7 translations included).