v0.7.0: behavioral insights — how was your week/month

New week and month modes: current span vs previous (tokens, calls, cache share, output share, list value, active days), 8 deterministic tip rules (pack expiry, peak-window burn, cache drop, premium-model drift, many-small-turns, single-day concentration, output spike, month pace), and a default GLM AI coach that reads aggregate metrics + fired tips and returns a verdict with up to 3 actions. --no-ai opts out (deterministic, free); --ai <model> picks the coach. Aggregates only are ever sent — no prompts or code. 42 tests.