535 lines, and it had already rotted: it named `repo.rs`, `pr.rs`, `browse.rs`, `key.rs`, `about.rs` and `review.rs`, none of which have existed since the module-layout refactor. Nothing went red, because it was the one long document outside `docs/` — so rustdoc never rendered it, `-D warnings` never checked a link in it, and `doc-lint.sh` never saw it. Most of the length was records rather than rules: 132 lines of what was verified by hand when each feature landed, 93 lines of per-fixture provenance. That kind of writing is stale the week after it lands and nothing checks it. What is left is four paragraphs of advice that does not go out of date — what earns a test, the two constraints that make parts of this crate untestable, fixtures for reads and mocks for writes, and an instruction to keep the page short. Moving it into `docs/` is the fix for the mechanism, not just the symptom: it renders with everything else now, and the twenty `see TESTING.md` references in `src/` became `[`crate::docs::testing`]` intra-doc links, which the doc build checks. Facts about one test moved into that test's own doc comment. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>