re: progress word B - search space closed at 21 functions, the field itself still unwritten

Section 5.3 left word B (+1956) with no known writer. Three routes ran this turn:
one produced a population, two were refuted, and the field is still unwritten.

The offset route has power here, unlike +184. +1956 is a large unusual offset with
9 stores and 28 loads image-wide, against +80's 5403 and 6923. Control: the known
reader 0x821898C4 sits in the gate's list-builder 0x82189870, exactly where 5.1
puts it. But none of the 9 stores turns out to be a progress write - filtering by
whether the storing function reaches the progress object gives 0 of 8 distinct
functions, and the 9th stores through r1, the stack pointer, so it is a local.
+1956 is simply an offset several unrelated structures also use.

The obvious filter is dead, and it fails its own control. Testing "does the
function reference the singleton global 0x828F48B0 or call 0x821707C0" against the
KNOWN word-A writer returns no contact, because that path reaches the progress
object through the copier and never through the global. A filter that rejects the
known-good answer proves nothing about the others.

What did work: progress is only ever changed copy-modify-store, so every writer
must call both the copier 0x82175110 and the setter 0x8216FF70. Measured, 21
functions call the setter, 21 call the copier, and 21 call both - the two caller
sets are the same set. That is the complete progress-write population and it is
small enough to read exhaustively. Control: the word-A writer is among them as
0x821C1630 (BASE_INFO + DIFFICULTY), and 5.2's store 0x821C1820 lies inside it -
the doc's 0x821C09D8-0x821C29F0 is the enclosing method, 0x821C1630 the function.

No member of the 21 stores to +1956 directly. Their only large store offsets are
into this - 1004, 1980, 2040, 2100, 2199, 2436 - with 1004 being 5.2's own
this+1004 & 0x20000 guard. So word B is written through the stack copy, at
localbase + 1876, which no offset scan can pick out.

One false friend worth recording: two of the 21 reference Points, which looks
exactly like the challenge record-storing path 5.3 predicts. It is not - their full
string sets are Dependency, MissionObjective, Points, WEAPON, WEAPONS, i.e. the
arsenal development economy, and neither references Time. There are two Points
vocabularies, development points and the leaderboard metric.

Next candidate, not yet checked: 0x8218EFE0 is the one progress writer whose
strings are BASE_EXTRA and DIFFICULTY - the only member of the 21 carrying the
EXTRA vocabulary.

All seventeen artefacts byte-identical.

docs/re/BACKLOG.md

@@ -7059,3 +7059,34 @@ is `16,24,25,26,27,28` — **`29` is a `MISSION_ID`, never a requirement**.
 🟡 `RECORD_TYPE`'s two values match the two ranking screens `POINT_RANKING` /
 `CLEAR_TIME_RANKING` by vocabulary, but no code path selecting one from that field
 has been shown.
+
+---
+
+## 🟡 2026-08-28 — word B's writer: search space closed at 21 functions, field still unwritten
+
+✅ **The offset route has power here** (unlike `+184`): `+1956` has **9 stores / 28
+loads** vs `+80`'s **5 403 / 6 923**. Control: the known reader `0x821898C4` is in
+the gate's list-builder.
+
+❌ **None of the 9 stores is a progress write** — 0 of 8 distinct functions reach
+the progress object; the 9th stores through **`r1`** (a stack local).
+
+❌❌ **The singleton-global filter is DEAD — it fails its own control**: applied to
+the *known* word-A writer it also reports "no contact", because that path goes
+through the copier, not the global. **A filter that rejects the known-good answer
+proves nothing.**
+
+✅ **The write population is exactly 21.** Every writer must call both the copier
+`0x82175110` and the setter `0x8216FF70`: **21 setter callers, 21 copier callers,
+21 in both — the same set.** Control: the word-A writer is `0x821C1630`
+(`BASE_INFO`+`DIFFICULTY`); §5.2's store `0x821C1820` lies inside it.
+
+❌ **No member stores to `+1956`** — their big store offsets are all into `this`
+(`1004`, `1980`, `2040`, `2100`, `2199`, `2436`). Word B is written through the
+stack copy at `localbase + 1876`, invisible to an offset scan.
+
+⚠️ **False friend:** `0x822A6B00`/`0x822A6EB0` reference `Points` but are the
+**arsenal development economy** (`Dependency`, `MissionObjective`, `WEAPON`), with
+no `Time`. **Two `Points` vocabularies.**
+
+🔑 **Next candidate:** `0x8218EFE0` — the only one of the 21 carrying `BASE_EXTRA`.