Give the failure module's two absences the reasons that hold, which are the request and the division of labour

src/failure/mod.rs

@@ -43,16 +43,45 @@
 //!
 //! # What is not here, said once so a green build is not read as covering it
 //!
-//! **No caller in this tree reaches any of it yet.** The transport is #27, the
-//! query surface is #39 and the artwork fetch is #49, so what exists today is the
-//! point and the suite that drives it. 0037 already says the honest proof that
+//! **No request is made anywhere in this library, so nothing here has been built
+//! out of an answer a server sent.** The transport is #27, the query surface is
+//! #39 and the artwork fetch is #49, so every value built today is built from
+//! something a module already decided. 0037 already says the honest proof that
 //! every failure went through this point is a check over the tree rather than a
 //! test, because a test proves the sites it reached.
 //!
+//! THIS SAID NO CALLER IN THIS TREE REACHED ANY OF IT YET, AND FOUR MODULES
+//! REACHED IT OUTSIDE EVERY TEST MODULE. [`crate::lifecycle`] builds a
+//! cancellation, [`crate::playback::handover`] builds 0111's refusal,
+//! [`crate::server::destinations`] builds a refused redirect, and
+//! [`crate::server::retry`] reads these variants to decide what a call does next;
+//! every one of those lines is above its own file's `#[cfg(test)]`. The sentence
+//! landed on 2026-08-28 and the first of the four on 2026-08-31, in a change that
+//! had no reason to open this header, with three more by 2026-09-03. The three
+//! issues named above were not what they came from: a module does not need a
+//! transport to build a refusal out of what it has already decided. Which modules
+//! reach this point is not carried here from now on, because a list goes stale on
+//! the next landing and nothing in this tree reads one:
+//!
+//! ```text
+//! git grep -n 'use crate::failure' -- 'src/**/*.rs'
+//! ```
+//!
+//! That names every module importing these types, a test module's own import
+//! included, so a reader who wants the library's own sites reads its line numbers
+//! against each file's `#[cfg(test)]`. #447 is where it was found.
+//!
 //! **The retry-after hint 0004 describes as given or assumed is carried as given
-//! or absent.** The assumed value is a delay 0038 decides and #38 is not built, so
-//! no number is invented here, and a caller sees the absence rather than a
-//! duration nothing chose.
+//! or absent.** No number is invented here, and a caller sees the absence rather
+//! than a duration nothing chose.
+//!
+//! THE REASON GIVEN FOR THAT WAS THAT #38 IS NOT BUILT, AND 0038'S POLICY IS IN
+//! THE TREE. [`crate::server::retry`] holds the attempt ceiling, the interval the
+//! first wait is drawn over and the deadline an attempt needs, and its own arm
+//! draws an interval where no hint was given, from 2026-08-31. What holds is the
+//! division of labour rather than an absence: the assumed value belongs to the
+//! retry policy, which is where a caller that has to wait reads it, and this type
+//! carries what the server said or nothing.
 //!
 //! **`answer-not-understood` carries where reading stopped as an offset and the
 //! reading it stopped inside, and not which field.** 0037 asks for the field as