feat(memory): validate temporal_decay_rate config value on deserialization #1777
Description
The temporal_decay_rate field in GraphConfig accepts NaN and Inf from TOML without validation. A NaN value causes degraded recall quality (NaN scores) without crashing.
Add clamping/validation on deserialization: reject negative values, NaN, and Inf. Clamp to [0.0, 10.0] range or error on invalid input.
Found by: security audit in feat/issue-1341 (SEC-T-02, low severity).