trendkit-core

Core types, SQLite snapshot store, source traits, and velocity scoring for trendkit.

• Subjects/observations: one append-only snapshot model shared by all sources (GitHub repos, HN stories, crates.io crates).
• Velocity: Δscore/day over a window, clamped to one hour minimum — single-snapshot subjects report zero rather than a fabricated spike.
• Deterministic time: all timestamps flow through an injected clock_kit::Clock, so collectors are testable with MockClock.
• Dogfooded: fetch-kit transport, retry-backoff schedules, clock-kit time.

See the workspace README for the CLI and full design notes.