Merge master into compare-rustynum-ndarray-5ePRn

Resolves add/add conflict on .claude/knowledge/vertical-simd-consumer-contract.md
by taking master's version (PR #149 — the polished READ BY / P0 TRIGGERS form
with agent routing). CLAUDE.md gains the W1a contract hard rule pointer
from master.

https://claude.ai/code/session_01EHNZhSmJ52FGyDxtCFgzXo

Author: claude