docs(accounting): the judge names the fidelity it does not check

Green: 112 passed in the gate's own file. The docstring now says what the two
routes do NOT reach -- neither decodes a pixel, so a converter writing a blank
PNG is accepted, and "claiming a conversion it did not perform" means claiming
one whose FILE is missing, never one whose pixels are wrong.

Teaching the judge pixels is a different job and is not this order. Leaving a
reader of the gate to infer the gap was the defect.

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

tools/okf_accounting_gate.py

@@ -440,6 +440,16 @@ def asset_holds(build: Build, source: Path) -> bool:
     says were written. A bundle claiming a conversion it did not perform still
     fails, which is the difference between reading the bundle and believing
     the report.
+
+    WHAT NEITHER ROUTE PROVES IS FIDELITY. Both ask whether a file in
+    `assets/` holds the bytes the bundle names, and neither decodes a PIXEL:
+    measured 2026-09-19, a mutated converter that writes a BLANK PNG is
+    accepted here, because the bundle is internally consistent -- the digest
+    it claims to have written really is the asset's digest -- and nothing in
+    this gate compares that picture with the source's. The suite fells that
+    mutant by decoding both sides; the judge cannot. So "claiming a conversion
+    it did not perform" means claiming one whose FILE is missing, never one
+    whose pixels are wrong.
     """
     digest = _sha256(source)
     if any(