Add OCR Accuracy section to README with field-level breakdown

Documents the 89.4% overall accuracy (up from 82.2% baseline, 95% target),
grounded in the actual logged run in accuracy_history.jsonl rather than a
vague claim, plus which fields the sanitize/triple-check layer rescues over
raw regex. Notes that current gaps are partly a photo-capture SOP floor
(DO paper photographed on top of other documents confuses auto-deskew),
not just a parsing/OCR ceiling.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017eRAsLqN9Sg1b9YPz22Lxz

README.md

@@ -12,6 +12,7 @@ No cloud OCR API is used. Everything (layout detection, text recognition, LLM-as
 - [Tech Stack](#tech-stack)
 - [Architecture](#architecture)
 - [How It Works](#how-it-works)
+- [OCR Accuracy](#ocr-accuracy)
 - [Repository Structure](#repository-structure)
 - [Getting Started](#getting-started)
   - [Prerequisites](#prerequisites)
@@ -114,6 +115,41 @@ For the full field-by-field extraction rules (fused-digit correction, date sanit
 
 ---
 
+## OCR Accuracy
+
+Accuracy is tracked field-by-field against 37 hand-labeled real DO photos (`backend/sources/test-images` + `manual_labels.json`), not a single vague "it works" claim. The latest logged run (`backend/sources/accuracy_history.jsonl`):
+
+**Overall: 89.4%** exact-field-match — up from an 82.2% baseline when this tracking tool was first built, against a 95% target.
+
+The bigger story is *where* that accuracy comes from. Raw regex extraction straight off the OCR text is only **67.7%** — the gain to 89.4% comes from a second correction pass: fuzzy SKU/store matching against master data, unit standardization, and format sanitization.
+
+| Field | Raw regex | After sanitize + triple-check | What closes the gap |
+|---|---:|---:|---|
+| Customer (Kepada Yth) | 100% | 100% | — |
+| Kode Barang (SKU) | 98.4% | 98.4% | Already reliable at the OCR layer |
+| Item count | 13.5% | 97.3% | Table-noise rows filtered by the SKU/unit triple-check |
+| Nama Barang | 0% | 94.4% | Corrected to master `sku_master.nama_item` on SKU match |
+| Banyak (qty) | 77.6% | 95.2% | Unit standardized from `sku_master.jenis_outer` |
+| Jumlah (total) | 76.8% | 94.4% | Unit standardized from `sku_master.standar_jumlah` |
+| No. PO | 91.9% | 91.9% | Fused-digit correction already applied at regex layer |
+| No. DO | 91.9% | 91.9% | — |
+| Tanggal | 89.2% | 89.2% | — |
+| No. SO | 86.5% | 86.5% | — |
+| Store | 0% | 64.9% | Fuzzy token match against `store_master` |
+| Plat Truk | 62.2% | 62.2% | Mostly genuine OCR misses on the truck-line, not a parsing gap |
+| Alamat | 0% | 37.8% | Canonicalized against `customers` table where phrasing matches |
+
+**Known gaps toward the 95% target:**
+- **Alamat (37.8%, capped)** — the ground-truth labels themselves use two different phrasings for the same physical address across photo batches; closing this needs the ground truth unified, not more parsing logic.
+- **Plat (62.2%)** — mostly genuine OCR misses (the truck line is often faint or absent in the photo) rather than a fixable parsing bug.
+- **Store (64.9%)** — bounded by the same `store_master` table noted in [What to Consider](#what-to-consider-before-you-install) — accuracy against it can only improve as far as that master data is populated.
+
+**A real factor behind these gaps is photo capture SOP, not just parsing or OCR quality.** A meaningful share of the current test set was photographed with the DO paper placed on top of other papers/documents rather than a plain, flat surface. That confuses auto-deskew: the pipeline estimates page tilt from the average angle of detected text blocks, and overlapping paper edges/text from the sheet underneath make that estimate unreliable, which is exactly the failure mode behind the unwarp-retry logic described above. In practice this means accuracy here is a floor, not a ceiling — tightening the field SOP (DO paper alone, on a flat contrasting surface, reasonably well-lit and squared to the camera) should raise these numbers without any further code changes.
+
+Reproduce this yourself with `backend/pfm-web-app/scripts/accuracy-check.mts` (`npm run accuracy`, or `--refresh-ocr` to force a real pipeline re-run instead of using cached OCR results) — see [Testing & Tooling](#testing--tooling).
+
+---
+
 ## Repository Structure
 
 ```