Record the eighth sweep, and count the cold dump's boxes properly

The sweep over the 6,300 lines of tests #19 adds, and over the seventh
sweep's own commit. Seven findings, in iris `77ed7a2`.

Also corrects a number four earlier rounds carried: the cold dump over 400
depth-5 trees is 34,488 boxes, not 34,492. The run prints eight lines that
are not a box, so `wc -l` gives 34,496 and a partial filter gives whatever it
gives. Nothing any round concluded moves, because each compared two dumps
rather than their line counts -- but the handoff now says how to count, so
the next round does not have to guess which figure was right.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/HANDOFF.md

@@ -6,8 +6,8 @@ found is in `docs/LAYOUT_LOG.md`.
 
 ## The Iris layout repair is submitted
 
-**Iris PR #19** (`layout/one-ask`) replaces closed #18. The tip is `f8aa0c5`,
-and past the reviewed `cadfba0` it is nine rounds, each described in
+**Iris PR #19** (`layout/one-ask`) replaces closed #18. The tip is `77ed7a2`,
+and past the reviewed `cadfba0` it is ten rounds, each described in
 `docs/LAYOUT_LOG.md`:
 
 - **The repair**, `add6774` and `84dad21` -- collapsed-share placement,
@@ -38,6 +38,12 @@ and past the reviewed `cadfba0` it is nine rounds, each described in
   arithmetic written a component at a time; a question asked through a value
   one line from its `&self` sibling; and `run-headless.sh --resize` leaving
   a replayed gesture scaled against the mode the output used to have.
+- **A sweep over the tests and the seventh sweep's own fix**, `77ed7a2` --
+  four shrunk fixtures naming one widget under three names and counting
+  each in the list of boxes the case compares, seven copies of a helper
+  sitting at the top of the same file, the GPU rigs' adapter probe written
+  twice, a mask resolved three times, a field nothing reads, a shrinker
+  claim its own assertion does not make, and three stale numbers.
 
 The settled design of the vocabulary rounds is in `docs/LAYOUT.md` under
 "Three names, and the one argument that says them". Bryan settled the API
@@ -93,9 +99,12 @@ the name it is reachable by.
 
 **Always**, because they cost nothing: format, workspace clippy under
 `-D warnings` with and without `layout-diagnostics`, the workspace tests, and
-the **cold dump**. `layout_dump` over 400 depth-5 trees is 34,492 boxes, and
-it is the only thing that catches two same-typed values being swapped, which
-is the failure mode of a rename or a move. The repair moved 650 of those
+the **cold dump**. `layout_dump` over 400 depth-5 trees is **34,488** boxes
+-- counted again on 2026-09-20, the fourth through eighth sweeps having all
+repeated 34,492, which is a `wc -l` of the whole run rather than of its box
+lines -- and it is the only thing that catches two same-typed values being
+swapped, which is the failure mode of a rename or a move. Count the lines
+that are a box (`grep -cE '^[0-9]+ [0-9]+ '`), not the output. The repair moved 650 of those
 boxes, all from the collapsed-share correction; every commit since has been
 byte-identical to `84dad21`.
 
@@ -114,6 +123,10 @@ a compile error, which reads exactly like a fuzzer failure.
    geometry and retained-primitive expectations. The seventh sweep is the
    evidence: reading `b7b8d09`, the sixth sweep's own fix, found that it had
    removed one dead operand from a test and left the one beside it.
+   The eighth adds a second lesson, about the tests themselves: a fixture a
+   fuzzer shrank is a regression test, so a round that rewrites one has to
+   prove the tree is the same rather than that the case still passes, since
+   a fixture that quietly changed still passes and covers nothing.
 2. **A review of everything written before the review gate existed.**
    `pre-submit-review` and the rule that nothing is submitted unreviewed
    arrived on 2026-09-13, well after the Rust port and most of Iris were