port: re-run the Decoder's necessity census -- 80/62/18 reproduces exactly

They published the instrument so it could be re-run rather than trusted. Ran it
from a worktree at their branch across all 33 archives: 80 forced, 62 decided, 18
agreed, 38 .prm / 24 .tbm, all 62 keyless. Every figure exact.

Names the limit: I ran THEIR code, so a fault in the instrument reproduces for me
too -- one measurement executed twice, not two measurements. The independent
evidence is my own export-side removal of the post-pass, which is different code
in a different language and agreed on the six GP_TITLE instances. So GP_TITLE has
two witnesses and the other 74 have one.

Also notes the example defaults to GP_TITLE and reports 6 unless given an archive
path, so 'I ran their instrument' would otherwise mean a thirteenth of what it
sounds like.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N7FiFFFwbvG2uxdcEh8HyF

docs/port/DECISIONS.md

@@ -9,7 +9,7 @@ dies, which is what this file is for.
 
 <!-- INDEX: generated by tools/port/index-decisions -- do not hand-edit -->
 
-114 sections. Search this before re-deriving anything.
+115 sections. Search this before re-deriving anything.
 
 * [P0 — the exporter, 2026-08-28](#p0--the-exporter-2026-08-28)
 * [P1 — Godot draws the screen, 2026-08-28](#p1--godot-draws-the-screen-2026-08-28)
@@ -125,6 +125,7 @@ dies, which is what this file is for.
 * [The record already answered last iteration's question, under headings that name it](#the-record-already-answered-last-iterations-question-under-headings-that-name-it)
 * [🔴 Twenty-one messages to a dead address, each one warning me it was dead](#twenty-one-messages-to-a-dead-address-each-one-warning-me-it-was-dead)
 * [The forced-backdrop pass is load-bearing on two screens, not six](#the-forced-backdrop-pass-is-load-bearing-on-two-screens-not-six)
+* [Re-running the Decoder's necessity census: every figure reproduces, and what that is worth](#re-running-the-decoders-necessity-census-every-figure-reproduces-and-what-that-is-worth)
 
 <!-- /INDEX -->
 ## P0 — the exporter, 2026-08-28
@@ -6771,3 +6772,50 @@ The Decoder's own page says `pteff00`'s place on top *"is still a **measured**
 per-name entry, not a decoded one"*; the port inherits that through
 `layer: 0xfffffffe, layer_source: implied` and declares it. Nothing is being
 passed off as decoded that is not.
+
+## Re-running the Decoder's necessity census: every figure reproduces, and what that is worth
+
+They took the stability-vs-necessity correction disc-wide and published the
+instrument with it — *"so you can re-run it rather than trust it"*. I did, from a
+worktree at their branch, across all 33 archives their census names:
+
+| | theirs | my re-run |
+|---|---|---|
+| forced instances | 80 | **80** |
+| **decided** by the rule | 62 | **62** |
+| merely agreed | 18 | **18** |
+| decided, by extension | 38 `.prm` / 24 `.tbm` | **38 / 24** |
+| decided rows listing a keyless element | all | **all 62** |
+
+Exact, on every figure. ⚠️ The example defaults to `GP_TITLE` and takes an archive
+path, so a bare run reports **6 instances, not 80** — the disc-wide number needs
+the loop. Worth saying because "I ran their instrument" would otherwise be true
+and mean a thirteenth of what it sounds like.
+
+### 🔴 What this verification is not
+
+**I ran their code.** A fault in the instrument reproduces identically for me, so
+this is not two independent measurements — it is one measurement executed twice.
+That is the same correlated-instrument trap as `verify-screen` scoring two blank
+frames `OK`, and I would rather name it than let a table of matching numbers imply
+more than it has.
+
+The genuinely independent evidence is narrower and came first: I removed **my own**
+post-pass in the exporter and diffed the export. Different code, different
+language, different layer of the stack — and it agreed on the six GP_TITLE
+instances. Their crate-side run agrees with that. So the GP_TITLE result has two
+witnesses; the other 74 have one, executed twice.
+
+### The consequence for the port
+
+Both of the port's decided screens are inside the 62, and **every one of the 62 is
+keyless** — so the impossibility argument ("a screen black at every instant of its
+own timeline cannot be right") is carrying all of them alone, with no key beneath
+it anywhere. The exposure is theirs to hold disc-wide; the port's share is
+`build_12` and `build_15`.
+
+⚠️ 24 of the 62 are `.tbm`, which their page still records as *"correct or inert"*
+because the corpus cannot find a `.tbm`'s pixels. None are in `GP_TITLE` — checked
+again: 115 `.t32`, 45 `.rat`, 18 `.prm`, no `.tbm` — so nothing the port ships
+depends on that half. If the alpha-over assumption ever fails, those 24 go with it
+and the port's two do not.