The Life of a User Message Inside Pi Agent — 26 Stations from Enter to JSONL

After you type «read README.md and tell me what this project does in one sentence», that string passes through 26 stations, crosses six npm packages, morphs across three message layers, and only then becomes scrolling tokens on screen and one JSONL line on disk. Cross-reading earendil-works/pi production source with hahhforest/pi-textbook's 15 checkpoints — every step's class hierarchy, event flow, owner roles, and diagrams laid bare.