Paper A v3.16: remove unsupported visual-inspection / sanity-sample claims

User review of the v3.15 Sanity Sample subsection revealed that the
paper's claim of "inter-rater agreement with the classifier in all 30
cases" (Results IV-G.4) was not backed by any data artifact in the
repository. Script 19 exports a 30-signature stratified sample to
reports/pixel_validation/sanity_sample.csv, but that CSV contains
only classifier output fields (stratum, sig_id, cosine, dhash_indep,
pixel_identical, closest_match) and no human-annotation column, and
no subsequent script computes any human--classifier agreement metric.
User confirmed that the only human annotation in the project was
the YOLO training-set bounding-box labeling; signature classification
(stamped vs hand-signed) was done entirely by automated numerical
methods. The 30/30 sanity-sample claim was therefore factually
unsupported and has been removed.

Investigation additionally revealed that the "independent visual
inspection of randomly sampled Firm A reports reveals pixel-identical
signature images...for many of the sampled partners" framing used as
the first strand of Firm A's replication-dominated evidence (Section
III-H first strand, Section V-C first strand, and the Conclusion
fourth contribution) had the same provenance problem: no human
visual inspection was performed. The underlying FACT (that Firm A
contains many byte-identical same-CPA signature pairs) is correct
and fully supported by automated byte-level pair analysis (Script 19),
but the "visual inspection" phrasing misrepresents the provenance.

Changes:

1. Results IV-G.4 "Sanity Sample" subsection deleted entirely
   (results_v3.md L271-273).

2. Methodology III-K penultimate paragraph describing the 30-signature
   manual visual sanity inspection deleted (methodology_v3.md L259).

3. Methodology Section III-H first strand (L152) rewritten from
   "independent visual inspection of randomly sampled Firm A reports
   reveals pixel-identical signature images...for many of the sampled
   partners" to "automated byte-level pair analysis (Section IV-G.1)
   identifies 145 Firm A signatures that are byte-identical to at
   least one other same-CPA signature from a different audit report,
   distributed across 50 distinct Firm A partners (of 180 registered); 35 of these byte-identical matches span different fiscal years."
   All four numbers verified directly from the signature_analysis.db
   database via pixel_identical_to_closest = 1 filter joined to
   accountants.firm.

4. Discussion V-C first strand (L41) rewritten analogously to refer
   to byte-level pair evidence with the same four verified numbers.

5. Conclusion fourth contribution (L21) rewritten to "byte-level
   pair analysis finding of 145 pixel-identical calibration-firm
   signatures across 50 distinct partners (Section IV-G.1)."

6. Abstract (L5): "visual inspection and accountant-level mixture
   evidence..." rewritten as "byte-level pixel-identity evidence
   (145 signatures across 50 partners) and accountant-level mixture
   evidence..." Abstract now at 250/250 words.

7. Introduction (L55): "visual-inspection evidence" relabeled
   "byte-level pixel-identity evidence" for internal consistency.

8. Methodology III-H penultimate (L164): "validation role is played
   by the visual inspection" relabeled "validation role is played
   by the byte-level pixel-identity evidence" for consistency.

All substantive claims are preserved and now back-traceable to
Script 19 output and the signature_analysis.db pixel_identical_to_closest
flag. This correction brings the paper's descriptive language into
strict alignment with its actual methodology, which is fully
automated (except for YOLO training annotation, disclosed in
Methodology Section III-B).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

paper/paper_a_methodology_v3.md

@@ -149,7 +149,8 @@ We use this only as background context for why Firm A is a plausible calibration
 
 We establish Firm A's replication-dominated status through three primary independent quantitative analyses plus a fourth strand comprising three complementary checks, each of which can be reproduced from the public audit-report corpus alone:
 
-First, *independent visual inspection* of randomly sampled Firm A reports reveals pixel-identical signature images across different audit engagements and fiscal years for many of the sampled partners---a physical impossibility under independent hand-signing events.
+First, *automated byte-level pair analysis* (Section IV-G.1) identifies 145 Firm A signatures that are byte-identical to at least one other same-CPA signature from a different audit report, distributed across 50 distinct Firm A partners (of 180 registered); 35 of these byte-identical matches span different fiscal years.
+Byte-identity implies pixel-identity by construction, and independent hand-signing cannot produce pixel-identical images across distinct reports---these pairs therefore establish image reuse as a concrete, threshold-free phenomenon within Firm A.
 
 Second, *whole-sample signature-level rates*: 92.5% of Firm A's per-signature best-match cosine similarities exceed 0.95, consistent with non-hand-signing as the dominant mechanism, while the remaining 7.5% form a long left tail reflecting within-firm heterogeneity in signing output (we do not disaggregate partner-level mechanism here; see Section III-G for the scope of claims).
 
@@ -160,7 +161,7 @@ Fourth, we additionally validate the Firm A benchmark through three complementar
   (b) *Partner-level similarity ranking (Section IV-H.2).* When every auditor-year is ranked globally by its per-auditor-year mean best-match cosine (across all firms: Big-4 and Non-Big-4), Firm A auditor-years account for 95.9% of the top decile against a baseline share of 27.8% (a 3.5$\times$ concentration ratio), and this over-representation is stable across 2013-2023. This analysis uses only the ordinal ranking and is independent of any absolute cutoff.
   (c) *Intra-report consistency (Section IV-H.3).* Because each Taiwanese statutory audit report is co-signed by two engagement partners, firm-wide stamping practice predicts that both signers on a given Firm A report should receive the same signature-level label under the classifier. Firm A exhibits 89.9% intra-report agreement against 62-67% at the other Big-4 firms. This test uses the operational classifier and is therefore a *consistency* check on the classifier's firm-level output rather than a threshold-free test; the cross-firm gap (not the absolute rate) is the substantive finding.
 
-We emphasize that the 92.5% figure is a within-sample consistency check rather than an independent validation of Firm A's status; the validation role is played by the visual inspection, the accountant-level mixture, the three complementary analyses above, and the held-out Firm A fold (which confirms the qualitative replication-dominated framing; fold-level rate differences are disclosed in Section IV-G.2) described in Section III-K.
+We emphasize that the 92.5% figure is a within-sample consistency check rather than an independent validation of Firm A's status; the validation role is played by the byte-level pixel-identity evidence, the accountant-level mixture, the three complementary analyses above, and the held-out Firm A fold (which confirms the qualitative replication-dominated framing; fold-level rate differences are disclosed in Section IV-G.2) described in Section III-K.
 
 We emphasize that Firm A's replication-dominated status was *not* derived from the thresholds we calibrate against it.
 Its identification rests on visual evidence and accountant-level clustering that is independent of the statistical pipeline.
@@ -256,7 +257,6 @@ From these anchors we report FAR with Wilson 95% confidence intervals against th
 We do not report an Equal Error Rate or FRR column against the byte-identical positive anchor, because byte-identical pairs have cosine $\approx 1$ by construction and any FRR computed against that subset is trivially $0$ at every threshold below $1$; the conservative-subset role of the byte-identical anchor is instead discussed qualitatively in Section V-F.
 Precision and $F_1$ are not meaningful in this anchor-based evaluation because the positive and negative anchors are constructed from different sampling units (intra-CPA byte-identical pairs vs random inter-CPA pairs), so their relative prevalence in the combined set is an arbitrary construction rather than a population parameter; we therefore omit precision and $F_1$ from Table X.
 The 70/30 held-out Firm A fold of Section IV-G.2 additionally reports capture rates with Wilson 95% confidence intervals computed within the held-out fold, which is a valid population for rate inference.
-We additionally draw a small stratified sample (30 signatures across high-confidence replication, borderline, style-only, pixel-identical, and likely-genuine strata) for manual visual sanity inspection; this sample is used only for spot-check and does not contribute to reported metrics.
 
 ## L. Per-Document Classification