Read protocol for agents

This file says how an AI agent shows that it has read the whole RCE spec, rather than claiming to. The spec is split into chapter files small enough to read whole. Each chapter ends with a footer holding the SHA-256 of its body and has one read-receipt question whose answer appears only in that chapter.

What the agent must do

1. Read every file spec/book/NN-*.md listed in INDEX.md, in full, in order. Skimming, searching or reading a summary does not count.
2. For each chapter, copy the hash from its last line (<!-- body-sha256: ... -->) and answer its Read receipt question from the chapter's text. Answers are short: a word, a name, a rule or a number.
3. Report the result as JSON, one entry per chapter:

{"files": {
  "00-overview.md": {"sha256": "<64 hex digits>", "answer": "<answer>"},
  "01-notation.md": {"sha256": "...", "answer": "..."}
}}

4. Say plainly which files were not read, if any. Never fill in a hash or an answer for a file that was not read.

How it is checked

rce-book verify receipt.json (in spec/checker: cargo run --release --bin rce-book -- verify receipt.json) recomputes each chapter's hash from the file on disk and compares each answer with a salted SHA-256 stored in receipts.json (the answers themselves are not stored anywhere). It prints PASS or FAIL per chapter and VERIFIED only when every chapter passes. Answers are compared after trimming, lower-casing and collapsing spaces.

A hash alone proves only that the agent opened the file; the answer shows it read the part that holds it. A correct receipt is evidence of reading, not of understanding. The salts are public, so a determined agent could guess short answers by hashing words from a chapter; doing that still requires having the chapter's text.

Keeping it valid

When a chapter changes, run rce-book build: it rewrites the footers, INDEX.md and spec/RCE-SPEC.md. rce-spec-check fails if the book and the single file are out of sync. If a change removes the text that answers a chapter's question, change the question and its salted answer in receipts.json in the same commit.