Measure [1.5] rather than leaving it reasoned, and say why it waits

The entry was written from reading the code. Measured now: adding a
brief to a step inside a `sequence` makes Root2JsonFixturesTest report
BriefDescription 2 -> 1 — top-level survives, nested does not. The
repro is two minutes and is written down.

The fixture change is reverted rather than left in the tree, because it
turns two suites red and a permanently-red gate stops being read.

Not fixed in the same session deliberately: closing it changes the JSON
INPUT surface's document schema, and [1.1] is Reid's open question about
whether that surface should exist at all. If it goes away the fix is
free and write-side only; if it stays, a schema change wants announcing
rather than discovering.

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

Author: reid-spencer

BACKLOG.md

@@ -671,6 +671,24 @@ that needs a ruling before either can be fixed.
   `JsonAstBuilder.nestedInteraction`, which exists to make the gap visible at the
   code rather than only here.
 
+  **MEASURED 2026-08-17, not reasoned** — the entry was first written from
+  reading the code, and this repo's own rule is that a claim about behaviour
+  needs a run. Add a `with { briefly "…" }` to a step inside a `sequence` in
+  `language/input/refusal-reason.riddl` and run
+  `riddlLib/testOnly *Root2JsonFixturesTest*`: it reports
+  **`BriefDescription: 2 -> 1`** — the top-level step's brief survives, the
+  nested one does not. That is a two-minute reproduction for whoever takes this.
+  The fixture change was REVERTED rather than left in place, because it turns two
+  suites red and a permanently-red gate stops being read.
+
+  **DELIBERATELY NOT FIXED in the same session that found it**, and the reason is
+  [1.1]: Reid asked on 2026-08-16 whether the JSON INPUT surface should exist at
+  all. Closing this means changing that surface's document schema — nested steps
+  going from `{"kind": …}` to `{"interaction": {"kind": …}, "brief": …}` — which
+  is a compatibility event for every consumer reading it. **Settle [1.1] first;
+  if the input surface goes away, this fix is free (write-side only), and if it
+  stays, the schema change wants announcing rather than discovering.**
+
 - **~~[2.2] superseded framing~~ (kept only so the reasoning is not re-derived).**
   **CORRECTED 2026-08-16 by Reid, and the previous framing was wrong.** This
   entry said the operand "should name an invariant, NOT prose", and offered as a