apply_feedback, decay, get_mean_affinity, and engagement_score had no
(or broken) test coverage. Also fixes decay(): subtracting a fixed
DAILY_DECAY from a score smaller than that step flipped its sign
instead of settling at zero, causing oscillation on repeated decay
passes.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KcD2BtNqehJxchKiuodTxi
Rust workspace with core (topic-affinity learning engine + relevance
scoring), db (sqlite/sqlx schema + repo), feeds (RSS/Atom fetch), llm
(rig + local Ollama embeddings/completion), and web (axum + Dioxus
fullstack UI, no separate JS stack). Two-stage relevance filtering
(embedding shortlist -> LLM judgment) and an engagement/surprise-based
topic affinity engine with daily decay. All crates compile and core's
affinity engine has passing unit tests; server and wasm client targets
of feedsignal-web both check clean.
